Meaning of "latest version, is not marked deployable so the web hook is not being invoked"

Hi there

I’m trying to using the webhook+API trick in order to add rows to a Reminders table when a new row is added to a Purchases one.
When testing the workflow rule using the audit log, I see that both entries of “REST API invoke” and “Change workflow rule” have a Result of Success.
But I don’t see the entry being added to the Reminders table and I can’t figure out why.
Is it related to this warning that shows in the log of the Change Workflow Rule action?
“Warnings”: “Warning: App version 1.000037, which is the latest version, is not marked deployable so the web hook is not being invoked. This web hook would have been posted…”
When I did the Deployment Check, I saw that there is one error only:
“Invalid subscription plan: …: User signin not allowed with the FREE plan, …Workflow rules not allowed with the FREE plan”

I’m still testing the app and I would like to see the new rows being created also in the reminders table as I want to add additional rules based on them before I deploy.

Thanks