Since no one else has mentioned it that I have found, it may somehow just be me, but after the latest update (file version 2.1.4.0, 66.0.3), PP Firefox will not load Gmail, as it did before the update. It just goes to a blank, white screen.
Win 10 64-bit
Same USB, E:\PortableApps\FirefoxPortable
Same computer
Haven't tried it on different machine yet. I will update if it is machine-specific.
Update: It is not machine-specific. It is showing a white blank screen for Gmail on all machines.
Update Update: I just solved the problem, by going into options, privacy and security, cookies and site data, manage data. I then removed the mail.gmail.com item, restarted the browser, and now Gmail is working.
Not sure why it glitched out after the last update...first time that has happened, but there's the fix.