Is it possible to be picked up for promotion in SelCon after being passed over twice for promotion to MAJ?

Technically, yes, but there's only a 2.8% statistical chance.

If you have been passed over you may want to look into moving to the reserve. You can pick up rank and volunteer for tours to get to retirement.

I know a guy who was passed over twice for LTC stayed on as a MAJ and picked up LTC 3 years later. He was #1 on the promotion list.