rollup field

[Sioks]

Hello. I am new to airtable. I have been using it for about a week now. I used the rollup field few days ago and it worked very well. Since yesterday I have been trying to use it but I get the same error message

Spoiler

"Sorry, there was a problem creating this field. The options are not valid."

I have the fields linked to another table but I don't get why it isn't working.

[TheTimeSavingCo]

Hmm could you provide a screenshot of the whole field editor please?  It seems to be working fine for me