My MS Word templates have disappeared

I use MS Office on my Mac with Mojave (v. 10.14.6). My Office version is 16.32.

I posted this cri de coeur in the MS Word forum, but it seems to me that the problem might be more an Apple one, so I am asking for help here, too.

Nightmare! My up-to-date Word templates have disappeared. When I open Word, the names and thumbnails of my templates appear under 'New'. The thumbnails show the correct templates, but in most cases if I double-click on one of them what opens has lost its heading and formatting. 

How can the thumbnails be correct, but the templates when opened be unformatted and without their headings?

This is a very recent phenomenon, more recent than the latest MS Office update. Can my templates have been moved to a new location in the update? If so, why cannot I open them in their proper format when I open Word?

A clue might lie in the fact that in (my name)/Library/Group Containers/UBF8T346G9.office/User Content/Templates there are what look like my Excel templates for my monthly domestic accounts, containing numerous regular payments, but they turn out to be old, out-of-date versions. Fortunately, I saved the up-to-date ones in a folder in Documents and can access them there.

Any help will be very gratefully received.

PS: To my even greater astonishment, I have now discovered that if I open old letters —copies saved in my 'Correspondence' folder — that I wrote in the past using my MS Word template, the headings and formatting have disappeared in them, too, even though they would have been saved in their proper form.