Why does one of my Quicken Classic accounts refuse to use a FIDELITY symbol I have inserted?

I'm on a Windows 11 laptop, using current Quicken version, I don't know when the problem started, but discovered it last week when comparing Quicken to my Fidelity account statements. I have found that one of my Quicken App accounts is not using a particular FIDELITY SYMBOL that I have assigned it to use in updating an Education 529 account item in Quicken. It is using a similar SYMBOL instead, resulting in a significant misstatement of the account current value. I have revised the account item several times with the correct Fidelity account SYMBOL, and the QUICKEN screen appears to have accepted my revision. After I close out the screen, I shut down and reboot the system.

I find that the revised SYMBOL has disappeared and has been replaced by the original, erroneous SYMBOL. I have Fidelity Education 529 accounts for each of my 5 granddaughters, and they all use somewhat similar Fidelity issued SYMBOLs. There is no problem with the other 4 accounts. I have even deactivated the problem account and restarted it, I have tried several times to get the correct SYMBOL inserted, I have rebooted, etc. and had no success. I have no problem with Fidelity's electronic or paper copy accuracy. I have been a Quicken user for over 20 years and never had a problem like this. What should I do now? All of the many other accounts I track with Quicken are perfectly satisfactory.

I'll really appreciate your help.

GEOFFREY FLETCHER, (Edited out personal contact information)