I have a multi-sheet spreadhseet, which has many goal-seek and solver
relationships, some activated by buttons to run code. I've been using this
sheet for doing calcs for over 12 months so I know that it works!

Today, for some reason the goal seek and solver functions don't work. I
don't get any error messages and it looks like it tries to do something, but
none of the cell values change.

I have tried using goal-seek manually from the menus and even creating new
formulae to test the function but nothing works.

I've tried rebooting (you never know!) but this didn't help.

Has anyone had this before? Any help greatly appreciated.