Website specific Adobe Flash not loading.

I have been having a pretty persistent problem with Adobe Flash on just one website.  I have never encountered this kind of Flash problem before.  I am using Firefox (latest verson 64 64-but) on a Windows 10 machine. Adobe Flash v 32.0 r0.  The website that I am working on is the citibank online site.  I am attempting to use one of the credit card features which invokes a pop-up window which uses Flash.  The pop-up is allowed for this site and so is the use of Adobe Flash.  The pop-up window opens properly and the Flash program begins to start ( as evidenced by a progress bar showing up) but then the flash program abruptly terminates.  At this point in time, the browser is completely frozen and I have to terminate the task using the Windows Task Manager..  I have never had this problem previously with this site.  And this is the only site where there is a Flash program that does not work.  It is very peculiar.

I have attempted what I would feel to be are the most straightforward fixes.  I have:

• tested my Flash installation (it works fine)
• Uninstalled then reinstalled Flash
• Cleared out all history and any cookies associated with the website
• changed the permissions and added exceptions to the security features in Firefox
• Refreshed Firefox
• Tested the website using the Edge browser application from Microsoft - it successfully called up the webpage and the Flash application
• Eliminated all security features on my computer (browser security, firewall) and this did not correct the problem

Right now, other than using another browser which does not completely rectify the problem, I am not at all sure what can be done.  Has anyone experienced such specific behaviors on a website and that is seemingly associated with Firefox freezing up?  Are there any particular settings that can be set with Adobe Flash that may rectify the problem?