Poor academic performance - should/can I apply to a PhD program?
You are now in your mid-thirties. You don't give a precise timeline, but based on your description I'll assume that the poor performance from the first university you attended for your master's happened about 10 years ago. In the meantime, you completed a degree elsewhere with much more distinction, and developed a career and a track record of successful achievements.

The logical conclusion is that any sensible admissions committee will look to your recent record as a much better indicator of your potential to succeed in the graduate program than your more ancient school history. The grades from your old school will very likely be seen as largely irrelevant. So, in my opinion this should not be a major concern.

And as @astronat said in a comment, you'll never know what would happen if you don't try. Good luck!