@ GT500 Thank you so much for your reply to my panic-stricken plea! I had sent three earlier emails over several days (via the link for support on the Emsisoft Home page) and couldn't understand how they went unanswered as this hadn't happened before - and I have been with Emsisoft for years and had no problem renewing things.
I had noticed that in this new Windows 10 free email (there simply aren't enough bad words in my Thesaurus to describe it!) that often it said it had sent emails but hadn't, so I developed the habit of sending bcc to myself; this way I found out that if my emails were in the Sent File then they really had gone - and all three earlier emails to Emsisoft were in the Sent File so presumably they had gone. David B says they weren't received at Emsisoft so they must have got lost somewhere along the way.
After writing my plea yesterday, I had the bright idea to phone which.co.uk computing - and they screen shared with me for over an hour and managed to get the licence key accepted (and chuckled in a kindly & sympathetic manner over my emails to Emsisoft evident increasing panic). I then started to write an email to Emsisoft to say all was well, but bethought me to check one last time that the licence was there, and there it was gone! So I turned off my computer and tried to resolve my migraine. I don't know where the details of my licence were hiding, but all seems well today - though I think it is going to be months before I really trust this system again!
Thank you so much for your help - it really was most kind of you.