Question

It isn't --- good talking to him.​

Answer 1

Both are correct but have different meanings. The first is an idiomatic expression.

It is no good talking to him - means talking to him won't work, he won't listen, he might be stubborn, for whatever reason taking to him is not any solution.

It is not good talking to him - isn't said as much as the first sentence. It's not good talking to him right now. Wait until he's calmer, wait for a better moment