The word right now is that WWE officials are not happy with CM Punk and the way everything has went down with his departure. Earlier it was stated that there were no issues between them but in reality, there are definitely some issues between them right now.
It may appear to some people that Punk's WWE contract expired & everything went smooth but that's not the case & WWE does not see it like that at all. This is not confirmed yet but WWE might be taking some kind of action soon against Punk for walking out on the company before his contract expired.
Earlier, CM Punk also talked about “never ever” wrestling again in an interview during Alternative Press Music Awards.
Here’s a video of Punk’s famous “pipe-bomb” from 2011: