At this point I would focus at least part of your time in the last hour of the day on the location that he was lost in. Be out there swinging a lure during that time of day until past dusk. By now he is probably back in that area all the time and you are just missing connecting with him. It sounds like the telemetry might not be working and you are going to be chasing dog collars for the duration. Telemetry is a useful tool, but the best tool you have available is knowing how the birds will react. I would depend heavily on that. I've chased Barbaries A LOT over the years in some very big country, and have learned that they are very loyal to the spot, even if their timing isn't very good!
Good luck and I hope you are able to connect with him again.