Hey @1875423, thanks for reaching our to us.
It sounds like this message is prompting you to install the Dropbox desktop app on your computer.
Are you trying to install the app or do you just want to access your files on dropbox.com?
If the latter, can you access them by going to this page?
Also, please send us a full screenshot of your screen, showing this message, so we can investigate further.
Thanks!