That message contains the reason for the error.
The provided checksum which is the string starting with "#" sign after the descriptor isn't correct.

Just change it with the correct checksum "g9v4p57c" and it will be imported to your watch-only wallet.

But if it's from listdescriptors command in your offline Bitcoin Core, the checksum should already be correct.
Anyways, check your setup if your offline wallet can sign the transactions created in the watch-only wallet.