I just had this happen again on my iPhone 13Pro with one of the podcasts I subscribe to. I've had it happen before with a few different podcasts' episodes, most recently while on a road trip that took me thru the SW USA. When it happened on the trip, I didn't have any cell service either, so couldn't attempt to fix it. However, I had plenty of podcasts and music loaded that were working fine, so I just listened to those. I'd forgotten about the problem until today when it happened.
I do have a VPN installed, but I don't turn it on when I'm at home.
After reading a few things others here said they've done to fix the issue, I first tried rebooting my iPhone, but that didn't help. Next, I decided to remove the non-playing podcast episode, then downloaded it again. It worked fine after that.