So they don't even say what "Settings" and yet blame Firefox? This is most odd itself they would at least tell you the where not just say go find and fix it. So back to the VPN are you logged in completely before you launch your Browser? What are the steps you do before you open your Browser when using your VPN? So did you disable any Addons before using it to access your Webmail? Sometimes VPN don't like Addons when access through a VPN. Edge doesn't allow many Addons and that's why it might work better compared to Firefox that allows more Addons to install.

In firefox, the only addons are Privacy pass and Ublock origin. The vpn is part of my boot up, and yes, I believe that it is completely enabled (expressvpn says I'm connected) before I go straight into firefox. Alan

Make sure you are not blocking content.

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop also see https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/

https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}