A lot of client turn Offline

A lot of clients are pointing to OLD SEPM server.. the old SEPM server is offline now and shutdown..

The effect is 9k of clients are Offline..

We know that the client is online (as my laptop is one of them). When i check the my laptop points to OLD SEPM..

Need assistance on how to do it to a lot of clients.

Our SEPM is sync to AD and each OU has its own policy (GUPS, USB, etc.)

thank you!a