I did see that, so it would seem to be a problem with the file. Possibly it is marked as read only?  Find X:\Lacerte\21tax\OPTION21 > Right Click and select Properties > Attributes > clear the read only and save

Go back and try the change (Tax program can be open when you do this attribute change)

Have you changed your fee charges from last year? If not, you could import the 2020 invoicing and get rid of it, but that would mean some time to redo them. Settings > Transfer Prior Year Settings...  > Select Client Invoice > Confirm the folder to copy to > Click OK