So a client had patched there 2 node S2D cluster this Sunday. When the 2nd node came up it would not join the cluster. So the client started troubleshooting, without realizing that the Quorum file share Witness was not working. Someone had managed to delete the folder where the File Share Witness was on. At first, the first node that was patched and booted was working. But at some point both nodes where booted over and over again.