Error creating contact via Zapier

Your software
My Mautic version is: 4.0.0
My PHP version is: 7.4.33
My Database type and version is: Mariadb

Your problem
My problem is:
I am trying to integrate Mautic with Zapier so that I can dynamically add new contacts to Mautic whenever a user registers on my mobile app through Firebase Auth.

So far connecting Firebase and Mautic has worked well with Zapier.
I am getting stuck at the step where running the test does not create a user in Mautic.

Any idea what might be going wrong here?

These errors are showing in the log:

Steps I have tried to fix the problem:

I had to turn the Zap on and off.