Worst case scenario Banker is that you cross threaded the protector (this is possible but not too likely). It is more likely there was a burr and the end of the threads and the protector is on the burr.
There are a couple of ways to get the protector off.
First do a complete safety check including shining a light down the barrel....
If you have a heat gun warm the thread protector (not the barrel) wearing gloves because the protector will be hot firmly grasp the protector and turn anti clockwise. It might just release like that.
Another method is to wrap the protector with cloth and use pliers and brute force to get the TP off but don't grasp the protector too firmly.....or use vise grips, again just get the grips tight enough to grasp without deforming the thread protector.
One or the other method should remove the protector.
Once removed check that there is no cross threading.....if there is you may need to get the protector rethreaded or the barrel.