Exaust manifold nut spinning with the bolt

I am replacing the gasket on the front exaust manifold, got it off, got the new one on, and putting the bolts back in, now on the last one, and I can’t get the nut to stop turning with the bolt, any suggestions? Cause I have tried everything that I can think of

You don’t mention the year of the vehicle. That makes it hard to suggest anything.

Are you talking the gasket between manifold and engine, or between the manifold flange and down pipe?