In this case I'm not saying the group name, I'm just in the room with the echo device and I say "Alexa turn on lights." In the groups Master Bedroom, Master Bathroom, and Kitchen it works. In the groups Sunroom, Office, and Camden's Room it does not work.
Your suggestion gave me an idea for a new test, though. The group Master Bathroom works with device Master Bathroom Lights, but I deleted this group and the Camden's Room group and switched the echo dots. Now Camden's echo dot is in the bathroom and the bathroom exho dot is in Camden's room. Now Camden's Room works and Master Bathroom does not. It is definitely the echo device that is the issue.