Firstly - this issue has been logged with support and is awaiting engineering review. Product support worked with me and we tried a number of trouble shooting steps before they escalated to engineering. In the meantime I'm looking to see if others have experienced this.
I can link my fr965 and my 67i and use the inReach remote system on the fr965 to send messages via the 67i. Everything seems to work as expected. I have tested with preset (check-in) messages and custom text messages. Everything works.
My issue is that if the 67i is powered down over night, and then powered up the next day, the pairing between the devices has issues. From the fr965 it shows its connected to the inreach, I can attempt to send a message from the fr965 and it looks like it was successful. However on the 67i the message never shows as arriving and never gets sent to the satellites (and thus never received by the recipients).
I rectify this by going into the settings on the watch, removing the inreach as a sensor and then re-adding it. After this it works fine until the next day.
I'm continuing to test to refine the pattern. For example, last night I didn't power the 67i down, and kept it within range (3m) of the watch throughout the night - and all seemed to be working this morning.
As I am the only person product support has heard from on this issue, I fully expect this is a user error, but maybe someone else experienced it and figured out how to fix it.