Cannot Change Inline Telephony Hook from Basic to OAuth 2.0

I am trying to setup a custom inline telephony hook. I originally tried using basic authentication with one service, but was having trouble, so I am now trying to do this with a different service which requires OAuth 2.0. When I try to switch between Basic and OAuth 2.0, I get the following error message: "Invalid Authentication Field and Secret. Must provide a non-empty header key and value"

These are fields on the Basic authentication tab. Not sure why its requiring me to enter these. I tried to go back to that tab, and my old values are there. But when I switch back to OAuth 2.0 and fill in all the required fields and try to save, it gives me this error. I am unable to change the authentication method from Basic to OAuth 2.0.

To complicate matters, Okta will not let me deactivate the inline hook I created (it says phone authenticator in use, must disable that first). I do not want to disable phone authenticator, as we have many people using it, so I cannot turn that off. And I am afraid to turn that off because I fear that I won't be able to turn it back on (its being deprecated this upcoming September), and then I'll have very unhappy users. I also tried adding a 2nd telephony hook, figuring I could test with at one instead and set it up new with OAuth 2.0, but when I try to save that hook, it says only one telephony hook is allowed. So I'm completely stuck.

Please help, thanks.