I had this exact same issue in my wife's Alltrack last week. My Moto G4 just wouldn't pair with the infotainment, so I disconnected from both my phone and the infotainment. I tried to re-pair but it just wouldn't detect the phone no matter how many times I tried. I even turned the car off briefly, then restarted it, but it still wouldn't find the phone.
What finally fixed it was to say fuck it, I went to work for 4 hours (and used my BT headphones in that time) then when I went back out to the car at lunch, suddenly voila, it could find my phone again and re-paired successfully.
I think you just have to leave the car off for at least a few minutes, otherwise the infotainment BT module never truly powers down. Also it would also help to restart your phone and maybe also pair it with another BT device beforehand.