I have not done extensive testing, but I believe that if someone sends a message to your 66i from your share.garmin.com/yourname website and enters his phone number in some formats other than 12345678901, then you will receive his message in a form to which you cannot reply on your 66i.
I believe you can work around this problem by deleting that thread (after writing down on paper his phone number and any information in his message that you need) and then starting a new thread addressed to his phone number in the "correct" format. You must delete the "bad" thread. If you don't, any subsequent reply from him will appear in the "bad" thread to which you cannot reply.
Hopefully, this post will soon become outdated. I informed Garmin of the problem on 7/6/21. If the problem is related to the phone number format, as I suspect, then it should be an easy fix on the share.garmin.com web site.
There was a similar problem on the explore.garmin.com web site when you entered phone numbers for contacts in a "bad" format. I believe that was corrected. I haven't checked. Does anyone know?
