Today I face with this error on Joplin-2.9.17 for Linux (AppImage). Latest version from GooglePlay works fine.
Steps to fix this issue:
- Disable encryption on both devices
- Clear local storage on affected side
- Send unencrypted data from non-affected side to remote
- Receive unencrypted data from remote on affected side
- Enable encryption on affected side (I change master password to new one), send encrypted data to remote.
- Clear local storage on non-affected side
- Receive encrypted data on non-affected side, enter new password