Why not :
group the tabs (click the first tab then the last while holding the Shift key)
enter the COUNTIF function in an occupied cell on the first sheet ( it will copy automatically to all sheets in the group)
Now on you master sheet use the SUM function with a 3D reference to obtain the final result
You can ungroup whenever needed

__________________
Using O365 v2503 - Did you know you can thank someone who helped you? Click on the tiny scale in the right upper hand corner of your helper's post