Here are some reasons why you might not be seeing your lookup field:
1. Missing a linked record field
When users are creating records, you will need to add the linked record field that the lookup relies on to the form as well. Lookup fields can’t work (display data) without a linked record in order to be populated, so users need a way to first link a record.
💡You can disable editing for any field in the form (including the linked record field). So it would be read-only. Prefills can be used to fill the linked field.
2. No linked record selected
The linked records field does not have any linked records selected.
3. Lookup field has no value
The linked record you selected does not have any values for those lookup fields.