Same here... I've been at a regional for six years (upgraded two years ago), and flew charter and corporate turbine equipment before that. I have 7-8 internals at each of the legacies, and LORs from CPs and LCAs at my current company.

I have zero checkride failures, and an engineering degree with a 3.5 GPA from one of the top engineering schools in the US. I have a long time history of volunteering for two different organizations. I've had my applications reviewed by two different prep companies (Cage and Emerald). I've been to several job fairs, met with recruiters, etc. They all said everything looks great. I had a Delta friend send an email to Delta HR last summer to have my app reviewed. I never heard a thing (no "fix it", so I guess at least my app was correct?).

I have apps out with United, Delta, American, FedEx, UPS, JetBlue, and Alaska. I haven't heard a word from anyone. It's definitely super awesome when I fly with a 20 something FO with no TPIC and they tell me about their United/Delta class date.

I don't understand it either. Fortunately my current gig is ok and I don't commute. Otherwise I would be considering grad school and a return to engineering. My wife is going to be a Nurse Practitioner in a couple years, and I may go back to school at that point if I'm still not able to move on.