Filter button grayed out when filters exist

Today I've found that the filter button isn't working when opening a saved sheet that already has a filter applied. I've opened a few saved sheets and they all have the same issue which you can see in the image below. Even though you can see that the column 'Today (filter)' has a filter applied to it, the filter icon is grayed out.


Even creating a new sheet and applying a filter to it also has the same problem.

Is there a way to resolve this issue or is it a back-end problem?

Answers