Form rules not working as intended

Form rules not working as intended

A small test on my part:

I created two additional fields for the 'Default Request' template: 'PO nr', 'PO send date'. These fields are not shown on the form initially.
Next i created a form rule, that stated: "show fields 'PO nr', 'PO send date' when 'category' is 'purchase'".

When i start a new request, set the category on "purchase", no fields become visible.

I tried a bunch of other things, but nothing seems to work on my part. If you guys want to check this out, via Teamviewer please, which speeds up things quite a bit and eases troubleshooting significanly.

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