I am attempting to set up event subscriptions for my company’s app - but upon saving the event subscription, there is no error displays but it does not allow me to save

Description
I am attempting to set up event subscriptions for my company’s app - but upon saving the event subscription, there is no error displays but it does not allow me to save.

Error
No error message. Cant save the change, in screenshot.

Which App Type

JWT, Webhook only, and possibly others.

Which Endpoint/s?

To receive QOS data

How To Reproduce (If applicable)
1.Steps to reproduce the behavior:
2.Create a JWT or Webhook app for your account.
3.Turn on and add a new event subscription.
4.Fill in the required info (Event listeners, Callback URL, etc).
5.Click save.

Please let me know if you’d like any more information, thanks!