Unable to create web apps with the app designer

Hello there,

Around 4 months ago, I was able to create web applications to one of our clients using the new app designer in the CRM, but for some reason that option is not showing up when creating a new app, it just shows up unified interface option.

Does anyone know why it let me to do it a few months ago and now is not available?

If this option was removed,  it was definitely a bad decision.

Thank you.