AutoFill Not Sticking

Hi Folks

Lately, Autofill has not been sticking to the necessary fields - username and password - on a regularly used site (banking) and the fields remain blank. The site then doesn't open. It will though open when the necessary fields are typed in manually. 

This problem has lingered for over a month but for years before that, all was OK.  No other sites appear to be affected.

Mac, Tahoe 26.4. Please note the problem began around (??) the time of the Tahoe update but I can't say for certain.

Cheers,

Volker