Since I spent I can't even count how many hours with TAC troubleshooting https inspection issues, I will list few things I always found to be a problem.
-when you see error like one you attached, first thing I always do is check pop monitor user command to see if access roles are matched (this ONLY if you use identity awareness)
-if you don't use IA blade, regardless, make sure the inspection rules have block user check enabled in the action column
-verify that trusted cert list is updated and valid
-in dashboard, make sure that you filter logs for https inspection blade and observe the message
Those are just some basic things to look at. Be free to message me privately if you need help, Im sure I could help you out with this,
Best,
Andy
"Have a great day and if its not, change it"