Hi @jmoreira_myp,
Thanks for the feedback.
So in your situation, the form control only can't work with the Custom API data source?
Have you checked with other data sources?
Please take a try to uninstall and reinstall the PowerApps studio, see if that would help.
If issue insists, please open the problematic app under PowerApps, navigate to
File->Account-Session Details
Copy and paste the Session ID here.
I will then formard it for further investigation.
Regards,
Michael