I’ve never switched from MAK to KMS, but I can tell you the KMS key is for the KMS server not the clients. The last I read that server key could only be activated 5 or 6 times, so you don’t want to activate it on your clients.
Try selecting “automatically select client KMS key GLVK” when you install a key. If that doesn’t work try manually installing the client keys.
KMS Client Setup Keys