Go to Logos.com, Account, Groups tab (4 tabs to left of account details, right under your name)
On far left, I found a hotlink that let me delete the Proclaim Beta test account I'd set up for my church. While it wouldn't let me change the group TYPE, it would let me delete it (whereas I couldn't in the Faithlife.com sphere).
Then, back in Faithlife, I was able to replace it with a new group. This time, I can change the group type within Faithlife.
Hope this helps someone else who was struggling with an old group that was created external to Faithlife & who couldn't delete it.