Dear Coenoby,
Thank you so much - at last someone who has actually understood the issue and given meaningful advice. I'm sorry to say that the VM advisors have failed entirely in doing this.
You are correct! I looked into that security setting and it was indeed set to Automatic sign out at 1 Week. I didn't know about that setting and have certainly never changed it.
I've now disabled it. However, when repeatedly signed out of webmail (whether or not due to this setting?) I was not then able to sign back in again. The only way I could access my email was to create a new PW (something one obviously shouldn't need to do on a weekly basis). That being the case, it would be hard to know whether or not this security setting was the cause of my issue.
To answer your question, during this whole debacle, I've never voluntarily signed out. I have only opened and closed the browser tab. For a period I could reopen that tab and access email but, periodically (after 1 week???), I'd open the tab only to find myself signed out and then I'd be prompted repeatedly, in an endless loop, to enter email and PW. It never actually gave a message that the details were incorrect, but I couldn't log in until I changed the PW yet again.
I'll have to wait and see whether changing this security setting resolves the issue. But to add to the mix, 2 days ago I finally managed to speak to a Second Line advisor overseas who (having assured me they knew what they were doing) told me they had made changes to the account that would resolve the problem; they wouldn't actually provide any details.
So, I can only hope and pray that either the actions of the Second Line Team or changing this security setting will result in my email functioning properly again, as it had done previously for years. If it starts working again I may never know which but all I care about is that it works!
NB I won't go into details as I feel like I'm suffering PTSD from all the time wasted on this but I should add that the issue has been far from clear, logical or consistent. There have been multiple factors - eg being able to log in on certain devices but not others and those then switching around, which I've found utterly bewildering. In addition, most of the time I've been able to log in on my Android phone but then, all of a sudden I couldn't.... and then I could again. Random and all over the place.
Perhaps strangest of all is the fact that, through all the recent PW changes made on my computer, I have nonetheless been able to go to the saved webmail "tab" on my home screen of my phone without having to log in at all. I'm no technical expert but how this is possible I simply cannot imagine. What a mess.
Anyway, thank you so much for replying and to giving proper thought and consideration to my intensely frustrating problems which, I know from other posts here, are not unique to me.
Sorry this is so long 🙂