Change redirect location based off SharePoint Group membership?

[nj]

I've seen other posts related to this and still cannot get it to work correctly. 

The way I was trying to do this was to display a different button depending on group membership. My conditional rule is:

not(fn-IsMemberOfGroup("Whale_Admins"))

Unfortunately, the button is still hidden even if the person is in this group. What am I doing incorrectly here?

[emha]

have you spelled group name correctly?

copy over rule's formula to a calculated value control a check how does it evaluate.

check developer console for any errors.