SMB connection to external Thunderbolt drive not working in MacOS Catalina After upgrading to macOS Catalina, I can no longer connect to one SMB drive from my MacBook Pro with MacOS Mojave. The share is stored on an external Thunderbolt drive.

It always shows an error message that shows that I don't have permission.

I can connect to other shares which are stored on the internal hard drives.
To solve this issue you have to do the following:

Open System preferences
Click on Security &amp; Privacy
Click on the Lock in lower left corner to unlock
Click on Full Disk Access
Click on the + button
Navigate to /usr/sbin
Seach for smbd and select it
Click open

Now the SMB daemon should have permission to connect to the external drive.