Can't open a Quickbooks company file

I’m trying to migrate from Boxcryptor to cryptomator. This is for a small business setup where all relevant files are hosted on two different cloud storage provider, Currently OneDrive and Dropbox. One essential component is Quickbook 2015 Premier, the accounting software I’m using. This works fine with Boxcryptor but doesn’t with cryptomator. I get to the login screen for Quickbooks and then a warning from Quickbooks:

We’re sorry. Quickbooks couldn’t open your company file.
We’ll try to fix the problem. Click Start to begin.

The “fixing” doesn’t work. The Quickbooks company file is basically a small database.

Any advise how to tackle this issue?