Hi Cary,
1. make an inventory of all userd with write access to the sheet and the author/owner using the big SHARE button on the top/right.
2. Left of the SHARE button you'll see all users which have the sheet open. This includes yourself ofcourse, maybe multiple times.
Have all these (open) users to close their browsertab(s) with this sheet.
3. start an incognito browsersession and login to Google with the account/owner of the sheet and open the sheet.
N.B. All the steps above cease any lock-conflict that may occur when multiple users (try to) alter the sheet/setup of FM.
And the incognito session rules out browser-extensions interfering with tabcontent or change browser behaviour (spamblockers or 'safety filters' sometimes obstruct big(ger) javascripts or alike code to be executed within the browser.
4. once "alone" in the sheet within an incognitosession, retry to access the menu's of FM and reconfigure any templates you like.
Template setups a stored as an hidden sheettab, which can be found in the list when you press the little burgermenu on the lower/left in the sheet.
HTH and all the best for 2023 to you all!
Cheers, Bart