Unable to add a FF in the condition within CSP

Summary:

When I try to add a FF in a condition within a CSP, I am not able to.

Content (required):

I am trying to add a FF to automatically progress a candidate to Assessment Scheduled when an interview slot has been confirmed (candidate selects an interview slot). I therefore, click the "+Fast Formula" button which then displays the "Condition" field as shown in below screenshot. But I am unable to select anything from drop-down or write anything directly.

Anyone know why this may be happening?

Thanks in advance

Version (include the version you are using, if applicable):

23C

Code Snippet (add any code snippets that support your topic, if applicable):