I had this issue and it WAS the internal probe (RTD Thermometer). I called Pit Boss, they sent a new one via pony express (meaning it took forever) so I ordered one from Amazon with one day shipping. Swapped it out and works perfect now. The one from PB eventually arrived and I keep it in case another fails.
To check your ignitor - remove grates, heat sheild, everything where you can see in the fire pot. Turn it on and watch it pellets feed. Then watch the ignitor. If it starts to turn red or you see smoke then it works. Do NOT touch it. Even if it doesn't turn red it could still be hot but more than likely if it doesn't turn red or if you don't see smoke then it is a bad ignitor.
My guess it is the internal probe. But if they are will to send you a new ignitor I would get one and keep for backup parts.
I do not know what kind of probe the 1150 has but if it looks like this then it should fit
https://www.amazon.com/SUNKISTCOOK-...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
Mine is a different type but I was able to find it on Amazon, also for 12.99. I would see if they will send you one for free to use as a back up, in addition to an igniter.
If you order the probe, just find one with fast shipping some of them are slower than others and it usually states when it ships. Many of them are one day shipping with Prime, others about a week