Hi rKelsey,
Thank you for posting your query in our community.
Based on your description, you want to Show / Hide fields based on choice field selection on SharePoint Online using formula. I tested your formula on my side, there was no problem. From below pictures you can see that once the formula for the field has been set, you will notice that it becomes grayed out. May I confirm that whether you have set the formula successfully?
If not, please try to manually enter the formula to see the result.
Best regards,
Jazlyn