How do I solve the "The server was unable to complete your request." nextcloud issue?

I started a nextcloud instand on a Linode back in July. Everything was running fine. I would access the nextcloud via a browser for using DavX5 on my phone. Now, when I login, I get the following error:

The server was unable to complete your request.

If this happens again, please send the technical details below to             the server administrator.

More details can be found in the server log.
Technical details

Remote Address: [I removed the address from this post]
Request ID: [I removed the ID from this post]

I tried restoring the Linode to a backup I made in August and it worked for a couple days but then I started getting the same error. I am not sure what caused it. I looked through all the nextcloud forums on this issue and most people had database issues or the wrong version of PHP. Does anyone have any suggestions? Thanks.