Initially when I launched the Survey123 template from AppStudio I received a "Invalid client_id" error message (Error 400).
I found this github article that I thought would provide me with the solution - though another error surfaced: Configuration for Launching Survey123 from AppStudio (invalid client_id) · Issue #401 · Esri/Survey123Community · GitHub
After reading this article I registered my app to create a client_id, entered/applied that ID in the advanced settings of the app in AppStudio and launched the app again.
Now, I don't receive the client_id error messages, but I do get a "Invalid redirect_uri" error message. I am not exactly sure what this is (other then something to do with OAuth) , but can tell you that this blank in the App Registration details in my AGOL account. I was hoping someone could help me to determine how I come up with a redirect uri
FYI: I was planning on having users sign in to this branded, Survey123 app with our AGOL account and not P.ortal.
Thanks in advance for any advice you could send my way to move forward!