OSD reads the Mavlink messages that have nothing to do with the hardware so it must not be sending that data anymore. I would check the serial configuration to see that it is enable to send those messages.
It could also be sending them as GPS2 instead of just GPS. Would need to see the mavlink stream to see what the messages look like.
What I discovered was that if port 3 was left at i think 5 for gps and not changed to something else like Mavlink the satellite data would not be displayed either on Mission Planner or OSD. The moment I changed Port 3 to mavlink and with that the baud rate to 57 the data would display normally