can't select from other sheet?

I’m trying to create a field “category” for the items in my sheet
the choices for “category” come from another sheet
I’ve created a field for “category” that links to the other sheet and when I create a new entry and click on this field, it opens a window that populates with the “categories” from the other sheet, but I can’t click on any of them and nothing happens no matter what I do
what’s going on?
if I change it to multi select it works fine and I can select these category entries, but I don’t want it to be multi select
I’m very confused by this

Hi,

We’ll need to check the problem in your database.

Click on the “Need Help?” at the upper right corner of your database. Fili out the problem that you encountered, including the sheet URL, fields, and steps with some screenshots or video, and send the support ticket to us.