68 b body master cylinder

Not getting fluid to come out of the front (Rear brake reservoir) of a rebuilt Master cylinder. In car and would like not to take out.
Thoughts

bench bleed on car, just be careful with your paint. could be a junk rebuild.

Cking directly at the master cylinder line connection ?

If nothing you need to pull it off , no way around that

Just had the same problem. It took me 3 masters to get a good one