Problem accessing MyCloudMirror after upgrading Mac OS to Big Sur

After upgrading my Mac to OS Big Sur, I have had problems accessing my MyCloudMirror NAS drive. TimeMachine can no longer connect to the TimeMachineBackups share on the drive. On my laptop, I cannot connect to the drive by clicking on the WDMyCloudMirror icon in the sidebar in Finder. I can connect using Command K + either the IP address or the name, but I cannot copy a file to the drive or edit a file already on the drive: I get an error ‘no free space’ on the drive, even though there is 1.55TB free.

Do I need to change any settings on MyCloudMirror to work with Big Sur?