I did not have this issue on my 2015 4Runner, but on my 2017 Tundra I did. I installed the Rago dash plate, which involved taking the radio out of it's place for a few minutes. When it went back in, the XM icon was gone. I had not unplugged any of the connectors, so I was a little confused on what could have happened. I took the head unit back out twice just to check connections, pulled the fuse, and even called XM and spoke to their ridiculous "advanced support team". In the end, all I did was pull the HU back out a third time and reseat the antenna connection on the XM part(the bottom) and then while the radio was still hanging in my hand I turned the truck on and there it was back again. I wiggled that connection and it went away. I wiggled it once again and it came back, so I carefully put the radio back in place and so far it's still on.
I hope that helps someone struggling with this issue. :guitar2: