Not possible to select user-defined formula on custom line rule

Summary:

Unable to select UDF in LOV for custom line rule in Receipt Accounting

Content (please ensure you mask any confidential information):

I have defined a test User-Defined Formula using a valid Source for the event class of Journal Line Rule, however it will not show in the LOV.

Is there some process which needs to be run?

UDF below. For a test I am even using the same Source as the seeded journal line rule uses.

However it does not appear in the LOV on a custom line type:

- Same application (Receipt Accounting)

- Same Event Class (Deliver to Expense)