OMFG you just can't win with this Mitel crap..
A real bug to make $$ for Mitel, wow such a genius company. Easier that fooling children.
I know many good fix around this bug...
1. Google Meet is free for a while. After the free period, its dirt cheap compare to AWC. Unsubscribe anytime.
2. Zoom is currently free for a while as well and same a Google Meet
3. GoToMeeting is same as above due to COVID.
4. Grandstream (6300 series) if you want a local PBX with AW Conferencing, currently the AWC is free until GS decides you need to subscribe, but i'll be cheaper that Mitel.
5. Conference Now, free audio conferencing. Use it in a pinch. I've used it many times it works just as good a paid, but you don't know if its secure.