Note: groups.io will be down for maintenance on Wednesday, October 5th, starting at 9AM Pacific Time (4PM Wednesday October 5, 2022 UTC), for approximately one hour.
Hmmm. Here's the strange thing although I should test it more thoroughly.
I sent a member a notice via the iOS Mac app for Groups.io. It gave me the green light that all was well and the message was sent. When I accessed our Groups site via a laptop, the "Draft" remained in that folder "unsent".
This needs more testing I'm afraid. I'll come back with hopefully an answer that "Yes! it was a refresh issue" or a some specific steps that are repeatable and show what's happening.