When I leave the 'SubDataF' form by clicking on the 'Close' button, I have an 'on click' event to close the form (DoCmd.Close) followed by requerying  the form/list (SubListF) to show the change (SubDataF form used to add a new record, requery the SubListF to see the new record). Again, this works in Copy1, but not in this copy - both taken from the same 'Template' db.

Asking the Chatgpt question.  

is the for SublistF open at the time of the execution?  If it's closed you will get that message.  

Is the name spelled correctly. Unlike X (formerly Twitter) correct spelling matters.  <---- Richard this is what I mean by saying Chatgpt can be cranky if Captain ChatGpt has had it's coffee. Or I didn't say please computer gods.

Could use a If Then to see if the form in question is open first. And if not Exit Sub.

Chatgpt says that sometimes Forms with Tabs or Conditional Loading won't load subforms right away.

When was the last time compact repair was done.  Just the other day I had a form that WAS working suddenly didn't.  I'd been tinkering (and I backed up tables and forms) neither the backup or the tinkered worked.  Compact Repair all was well(ish).

I would move the code to the On Close event.

Kevin Robertson is the winner...I thought for sure I tried this with no success...maybe I tried a variation of this? - I can't recall. In any case, I moved it to 'On Close' and it's working.

Jeffrey Kraft - Spelling and everything was/is correct - I checked against the table name itself as well as another button that opens the SubListF form. The only thing I did not do was to 'Compact/Repair' - I did this and still no luck. Now...to be fair, after I ran teh 'Compact/Repair' and didn't see any change, I did do Kevin's suggestion by moving the code to the 'On Close' event...that worked. I can't say if the 'Compact/Repair' had anything to do with it or I simply never tried that option - just trying to be as open as possible.

In either case, problem seems to be resolved so I thank you for your help!!!!!