[itimpi]

As far as I know there is no way to fix the issue with DropBox. It is a result of a decision by DropBox to discontinue offering a facility they used to support.

Google Drive might still work - this will need checking out. I have heard rumours that they may also be changing what they support but have not checked it out. Note, also, that Google Drive will cause problems with Calibre if you try to use it to sync a Calibre library between computers. This is mentioned in the current Calibre2opds documentation in the section on setting up Google Drive for use with Calibre2opds.

I think I might look into whether it is possible to use a hybrid solution where the Calibre2opds catalog is hosted on Google Drive while the main Calibre library remains on DropBox. This just might work if you only go to dropbox to download the actual eBook files. It would also remove the risk of corrupting your Calibre library by trying to host it on Google Drive. I will provide feedback on whether I can get this working.