I understand that you are only repeating what you were told.
Obviously I was unaware that you had Roboform installed on one computer let alone on all the computers that you used to test to see if you were having the problem on other web browsers, PCs and on a different network.
If you have Roboform installed on all the devices and you are having the problem on all the devices except when you uninstall it from the devices then it would obviously appear to be Roboform causing the issue however I have no idea why that would be the case other than it must be corrupting your email account in some way.
RoboForm requested that I send them a video screenshot!! After taking all evening attempting this I finally did it! They have just now come back with a suggestion which I will try. I will report back.