Why will it not let me trust developer on my iPhone XR

Hello Queenb2293,

Welcome to Apple Support Communities!

If we understand your post correctly, you're unable to trust a developer on your iPhone. We'd like to help!

The article below will provide you with steps on how to manually trust an enterprise app.

Install custom enterprise apps on iOS

Let us know if you have any questions.

Thank you for using Apple Support Communities.

Take care!