Take a look at your Budgets History sheet (hidden sheet usually) and see if there is a lowercase “groceries” column to the far right with some amount for one of the lines there. If so, just delete that column and then run Analyze Budgets History from the Add-ons menu > Envelope Budget > Envelope Budget
At first I wasn’t able to delete the bad column ‘groceries’ because I had a transaction miscategorized as ‘groceries’ instead of ‘Groceries’. I found the bad transaction and re-ran Analyze Budget History. All good.