@panixia
Normally that is my workflow as well. Everything goes to "Untagged".
In this case, I got a .dwg site plan with all kinds of information and the existing tags were the only way for me to know what was what.
So I was picking each tag, selecting the geometry, re-tagging it to "Untagged" and then grouping it and putting it on my own tag system.
There was a 2d topo map that I did convert but they also provided an elevation accurate set of topo lines that forgot to process. I just grouped it and then went straight to toposhaper. I was in a rush I think.
That group was also inside another group. Solution was as @fredo6 said, put the group by itself, fixed the geometry tagging and then run the tool. Have a nice healthy terrain now.