Check and document (here), if the other web- / cloud-storage options still work: Box, Google Drive, OneDrive, WebDAV (used by e.g. OwnCloud / NextCloud)
Note that Dropbox is known to fail, but nobody has yet tried to address it: See issue #4 for details.

For each one which fails, concisely denote what is failing (login, file transfer etc.) and provide the exact error message, preferably as copied text (alternatively as a screenshot). Also start FileCase at the command line (simply type filecase), repeat the action which results in an error and copy & paste the relevant output here (i.e ignore all the output at application startup).