Cannot upload files to share - CrossClave 19.0.0 with Linux Mint 20

I installed CrossClave 19.0.0 build 27 on Linux Mint 20 with a free license key.
I can create a shared space with new folders, invite others to the space, and chat.
But I can’t upload files (photos, docs, etc.) to the shared space or folders from within the Linux app and get an error message:
“There was an error when trying to upload “[file name]” to #Shared_space. Please try again or contact an administrator.”

I CAN upload files to the shared space from a Windows version of CrossClave as another user and can then see the files from the Linux side.

What can I do to troubleshoot this?
Thanks.

Similar applies to 19.0.0 on Linux MX-19. All worked well until the (forced) “upgrade” to the latest CrossClave version, but now there is a problem uploading modified files, and an error when attempting to close the app.
Screenshot_20220401_154919
I too would welcome help on troubleshooting this.
Thanks.

And here’s the error message when trying to upload a modified file:Screenshot_20220401_155103