yes, I tried this in Classic. I didn't manually add fields just places checkmarks next to the boxes in Configure Attributes so that might be the missing link (so to speak).
And, yes, in Enterprise not just Online which is a new platform to me used by my present employer.
I added the fields manually within the Text box and this is now working with the email link and columns showing in the popup. I had thought adding them through the popup Configure Attributes link was the correct approach.
I can't thank you enough for this Katherine. I will be making notes of this process for future reference and sharing with my colleagues.
Again: thank you and have a wonderful day.
Rob..
I'm glad you finally got it to work! I believe the fact that you are doing this in Enterprise instead of AGOL is the answer as to why you don't have the "Source" option in New Map Viewer. (depending on what version of Enterprise you're running....but AGOL will always be the most current because it is updated by Esri).
Anyway, yes, seems like in your case, configuring in Map Viewer Classic is the way to go, even though it's unfortunately a bit cumbersome with manually adding those fields.
Glad I could help!