Oury, Thank you so much for the help.
I'm not entirely sure if it was regenerating the key that fixed it or I fixed a rather silly mistake on my part. I'll swallow my pride and post what I did in case it helps someone else.
I setup a super simple test case in C# to eliminate the variables and try to authenticate both way. I reset the key then clicked the copy button for the connection string. When I pasted the connection string into my code, the value of the clipboard was literally:
*********************************************************************************************************************************
I had thought that when I pasted the connection string into the third party tools, it was masking it like a password field... it wasn't.
I had to click the eye icon before clicking the copy icon in order to copy the actual connection string.
Now I just need a way to tell my client that the problem is fixed without sounding like a dufus.