Can an AC officer obtain a Reserve/Guard commission after being twice passed over for MAJ?

I was passed over in the AC and went to the RC and did OK for myself...

Yes, it happens all the time, but the component still has to accept you. I was the CM USAR Career Manager and we routinely had AC 2x NONSELs come over into the traditional reserve TPU (USAR) system. The USAR still has a substantial amount of billets to promote into, in your case to MAJ>LTC. Just make sure that you knock out ILE, at least the common core, as soon as possible. There are several ways to get it done. Talk to the silver siege officer at your installation or regionally. You can get this POC from the RC career counselor's office or the servicing Army Reserves Career Division BN. Good luck!

I got tossed from AD when the selection percentage was 13-15% for those who were CEC for 10 years in favor of line staff transfers. So that meant my record at the next board on the Reserve side was quite different from the folk who were reserve all the time. So I picked up O-4 on the first look and went on from there. The AD side's loss was the Reserve side's win. Turned out to be a blessing in disguise when things started going South in the sandbox in the 90's. We had very capable and deeply experienced officers who performed well.

BTW, the fruit salad mania that has perversely been allowed to run wild is a detriment that allows reporting seniors and board members to be lazy. It obscures the real performance levels and capability of the SM. A perceived ratio problem becomes an easy reason to toss at third crunch time. That's why SMs closer to the flagpoles tend to fare better. They get more anointment and ointment.