I am receiving the following error when I try to gain authorized access to the API: Uh oh!
An invalid scope name was provided. Please contact the integrator.
This looks like it might be a simple typo here. The scope name is transactional-email (singular) and it looks like you have an "s" on the end of the scope name.
Would you mind trying that and seeing if it works? If not there might be something else going on.
You're 100% correct, the typo was the problem. However, in order to make it work, I had to remove all of the "Read from and write to my" selections. Is that normal?
In this case, yes that is normal. Checking those would require you to request those scopes in the OAuth flow. It's a kind of a check on your own app to make sure you request the scopes you actually need.