Invalid_Grant whlie generating Access Token using saved Refresh token in Dropbox Sign .NET SDK

Question

Hello Greg-DB&nbsp;,
&nbsp;
I am using the following Dropbox Sign .NET SDK code in my project to generate Dropbox Sign Access token using previously saved Refresh token.
&nbsp;
&nbsp;public async Task&lt;TokenResponse&gt; GetRefreshToken(TokenResponse tokenResponse)
&nbsp; &nbsp; &nbsp; &nbsp; {
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; TokenResponse tokenResponse2 = new TokenResponse();
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; string errorlog = ConfigurationManager2.AppSettings("ErrorLog");
&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var config = new Configuration();
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var oAuthApi = new OAuthApi(config);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; try
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var data = new OAuthTokenRefreshRequest(refreshToken: tokenResponse.RefreshToken);
&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var result = await oAuthApi.OauthTokenRefreshAsync(data);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (result != null)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; tokenResponse2.Expires = result.ExpiresIn;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; tokenResponse2.AcquireTime = DateTime.Now;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; tokenResponse2.AccessToken = result.AccessToken;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; tokenResponse2.RefreshToken = result.RefreshToken;&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; tokenResponse2.AcquireTime = DateTime.UtcNow;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return tokenResponse2;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; catch (ApiException ex)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "

" + "nGetRefreshToken: - Error");
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "
Exception when calling Dropbox Sign API: " + ex.Message);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "
Status Code: " + ex.ErrorCode);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "
Stack Trace: " +&nbsp; ex.StackTrace);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; throw ex;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; catch (Exception ex)
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "
GetRefreshToken - Error");
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; File.AppendAllText(errorlog, "
" + ex.Message + "
" + ex.StackTrace);
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }
&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return tokenResponse;
&nbsp; &nbsp; &nbsp; &nbsp; }
&nbsp;

I am getting the following Error Message and Stack Trace.
&nbsp;
Error converting value "invalid_grant" to type 'Dropbox.Sign.Model.ErrorResponseError'. Path 'error', line 1, position 24.at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureType(JsonReader reader, Object value, CultureInfo culture, JsonContract contract, Type targetType)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)at Dropbox.Sign.Client.Configuration.&lt;&gt;c.&lt;.cctor&gt;b__78_0(String methodName, IApiResponse response)at Dropbox.Sign.Api.OAuthApi.OauthTokenRefreshWithHttpInfoAsync(OAuthTokenRefreshRequest oAuthTokenRefreshRequest, Int32 operationIndex, CancellationToken cancellationToken)at Dropbox.Sign.Api.OAuthApi.OauthTokenRefreshAsync(OAuthTokenRefreshRequest oAuthTokenRefreshRequest, Int32 operationIndex, CancellationToken cancellationToken)at SGCloudMigration.Business.DropboxSignUtility.GetRefreshToken(TokenResponse tokenResponse, String relationshipname) in D:\SG Cloud Migration\SGCloudMigration.Business.Core\DropboxSignUtility.cs:line 364
&nbsp;
Please&nbsp; help.
&nbsp;
Thanks,
Gagan

Spencer H · Accepted Answer

[Cross-linking for reference: https://stackoverflow.com/questions/78296262/why-am-i-getting-invalid-grant-error-while-using-refresh-token-to-generate-acces ]
&nbsp;
Hi Gagan,Thank you for reaching out, it looks like you are receiving an&nbsp;invalid_grant&nbsp;error. This error typically occurs when using a stored refresh token and one of the following is true:&nbsp;&nbsp;- Scopes for the OAuth API app have changed&nbsp;- The user revoked authorization to the OAuth API app&nbsp;- The OAuth API app is approved multiple times by the same user—this will cause the previous authorization to reset and a new refresh token to be generated.If any of these actions have occurred, please try completing the authorization process again for the user to generate a new&nbsp;access_token&nbsp;and&nbsp;refresh_token. Try using the new&nbsp;refresh_token&nbsp;to generate any new&nbsp;access_token&nbsp;after the initial&nbsp;access_token&nbsp;expires. Please see our&nbsp;OAuth Walkthrough&nbsp;documentation for more details.If the issue persists, please&nbsp;submit a support request, along with the code snippet you just provided, so we can further assist you in determining why that error is being thrown. Thanks!