I was building a spreadsheet to count various items automatically. I was using "COUNTIF" to look for instances when cells contained certain letters and add up the totals for the different letters. Last night it was functioning great, counting the letters as I adjusted amount of letters. But today, each cell with a COUNTIF function stopped working and won't update at all.

In some of the cells, but not all, I was setting a new rule where the cell would change color based on how many of a certain letter appeared in the range we were looking at. Those with the new rule were working fine last night as well, but now none of the COUNTIF cells are working, regardless of if there was a new rule.

Any ideas what could have caused this?