Calculated rollup error, manually recalculate doesn't work

My opportunity form has a calculated rollup field to get the sum of estimated $ amounts of different items in the opportunity. One user is reporting issues, nothing happens when he clicks the manual recalculate button. I set up a test account with the same security role. I went to an opportunity he reported having issues, I was able to recalculate manually without issue. 

Anyone seen this error before?

Is there a limit to the number of times I can use a rollup field? I have 1 rollup field but 500+ opportunities entered.

Thanks