59 CJ5 no brakes

Good morning everybody!
I put a new master cylinder in my 59 CJ5 a month or so ago. Brakes worked great until last week when I lost all pedal. There are no signs of leakage, haven't checked the fluid in the master cylinder yet. Gonna bring it back in the barn today to start looking into it. It has a brake booster, I believe that's what it is.
Could there have been air trapped somewhere in the system that could have finally worked its way into the brake lines maybe? Or could the new master cylinder have gone bad already? I only drove it maybe 5 miles on my property.
Thanks!

Hey Joe! Does it pump up or is the pedal gone completely? Is there still fluid in the master cylinder?

A few things could have happened but, if you haven't lost any fluid and it wont pump up I do suspect the master cylinder.

Does you your CJ have swing pedals?
Is the master cylinder mounted on the firewall or is it mounted on the frame below the tub like the old style Jeeps?
If it has a brake booster on it I take it is mounted on the firewall and you have swing pedals, you may want to check for a vacuum leak to the booster somewhere and narrow it down to see if your booster may have went haywire.
Just throwing that out there for some thought.

That's what I'm guessing, but I just put a new master cylinder on it about a month ago. I'll probably upgrade it to a 2 chamber master now.
Thanks for the reply.