Since the update to MacOS Catalina you need to give specific permissions for applications to write to your Nomadesk vault. This is related to the fact that older vaults are running the encrypted SolFileSystem.
You can resolve this via 2 options:
1. (preferred method!) remove and re-import the vault locally: this will re-import the vault as a Sparse image file instead of a SolFS data file.
2. add the progams (eg Word, Excel,...) that you want to allow to write to your vault via Full Disk Access under Security & Privacy.