GetRESTProxy returning INVALID_FUNCTION in CXone Studio

fails with INVALID_FUNCTION. Tried every syntax variation.

ASSIGN rest = GetRESTProxy("https://api.niceincontact.com")

ASSIGN rest = GetRESTProxy("https://api.niceincontact.com/api/v2")

Both throw error. version is latest. Is the function name case sensitive? Or is the endpoint format wrong? Logs show nothing helpful. Just generic script error. Need working example.