Can't update a field on a parent form from a child form's On Success workflow

Can't update a field on a parent form from a child form's On Success workflow

Title: Can't update a field on a parent form from a child form's On Success workflow

Hi everyone,

I'm building a simple Golf Lesson Tracker app and I'm stuck on what should be a basic operation — updating a number field on a parent form when a child form record is submitted.

Here's my setup:
- Students form (has a Number field called Lessons_Remaining)
- Top-Up Log form (has a Lookup field to Students, a Picklist called Package_Type with values 5-pack/10-pack/20-pack, and a Date field)
- Lesson Log form (has a Lookup field to Students and a Date field)

What I'm trying to do:
When a Top-Up Log record is submitted, I want to add the corresponding number of lessons (5, 10, or 20) to that student's Lessons_Remaining field.

What I've tried:
- Workflow on Top-Up Log form → Created → Actions on successful form submission → Deluge script
- I've tried rec.Lessons_Remaining = newTotal using a for each loop to fetch the student
- I've tried studentRec.Lessons_Remaining = newTotal after fetching with Students[ID == studentID]
- I've tried zoho.creator.v1.updateRecord
- None of these update the Students form. No errors — the value just stays at 0.
- I confirmed the workflow is enabled and set to On Success (not On Validate, which was an earlier mistake)
- I even tried a brute force test setting ALL students to 99 — still stayed at 0

The script runs (I confirmed because an alert command threw an error saying alerts aren't allowed in On Success workflows), but the student record never updates.

What am I missing? Is there a permission or setting I need to enable for cross-form record updates?

Thanks in advance!