New master cylinder, brake pedal on floor next morning??

I had 1/2 dozen reman'd master cylinders fail, practically during the bench bleed process ( or so it seemed ). Luckily they were from the local part counter where I could take back all most as fast as it failed.
I did recently buy a master cylinder online, Rockauto or Amazon I forget. It is/was a new one though. So far so good. Good luck with yours.