Product: Credit reporting, credit repair services, or other personal consumer reports

For many years, Ive had a freeze on my credit with all 3 bureaus ( Experian, XXXX, XXXX  ) and have many times successfully thawed my credit when applying for loans or credit cards, both online and using my phone. On XX/XX/2020, I thawed my credit with all 3 bureaus successfully in order to apply for a mortgage refinance. 
At closing XXXX XX/XX/2020 XXXX my mortgage company required a recheck of my credit, so I was asked to thaw my Experian credit freeze only. When I tried to do this ( in the EXACT same way and using the exact same PIN as on XX/XX/XXXX ), Experian would not thaw my credit and gave the message, PIN is a required entry. I reentered my PIN and got the same message. I then tried to use the phone method, but the message there ( after entering correct personal info and PIN ) was that I would have to request my thaw by mail. Luckily, my mortgage company was able to use XXXX  instead ( which thawed easily ) or my mortgage would have been held up for possibly weeks or longer. 

I waited a few days and on XX/XX/2020, tried to thaw again ( thinking that after a few days, my account might reset ), but still got same message. I tried to figure out how to contact Experian via email or phone about this problem, but they provide no email address and the phone number provided would not allow me to actually talk to a person. I searched the web to find other phone numbers and eventually got to a real person. I explained my problem and they said I must have used the wrong PIN ( which I did not ). I told them that the Experian message was PIN is a required entry, not wrong PIN, but they insisted on sending me ( via mail ) a new PIN, which I received on XX/XX/2020. I tried thawing my credit using the new PIN and got the same PIN is a required entry message. I was using the XXXX browser to do this, so I tried using the XXXX browsersame problem. I tried using their phone thaw method and was again told ( by a robot, not a person ) that I would need to send in a request using US mail. My new PIN ( like my old PIN ) was not the problem. There had to be something else that was causing the problem. 
I again attempted to call Experian and finally ( after trying several numbers and working through there menu system ) got to a real person XXXX XXXX XXXX. XXXX said everything looks right from his end, but had never heard of the PIN is a required entry message. I asked if he could connect me to someone in technical support to try and identify what that message meant. He went on hold to talk with his supervisor, then came back and said that Experian does not have technical support. I said that somebody had to create the website and that at least HE must have some way to get technical support and he said no. I told him that I really just wanted to get this fixed so I wouldnt have problems the next time I needed to thaw my credit. I told him that if Experian could not help, I would need to file a complaint with someone to get action and that I would just prefer to have Experian provide some technical support. He again said there was nothing he could do. I asked to speak to his supervisor. XXXX said he would and put me on hold. After several minutes on hold, XXXX returned and said that there was no supervisor available and that I would just need to file a complaint. 
All I am requesting is that someone at Experian tell me what the PIN is a required entry means ( when PIN number is entered correctly ) and fix this problem so I will be able to freeze/thaw my credit in the future.