Owner's manual HERE: http://stevespages.com/pdf/remington_572.pdf
Odds are, there is a problem somewhere is the trigger/sear connection- spring may have SPROINGED on you.
Make sure rifle is clear, cock, tap out those two pins, remove trigger group, clean with spray Gunscrubber or the like, and lay the M1 eyeball on the parts. RESTRAINING THE HAMMER with your thumb so that it does not slam forward, eyeball the parts, see what is out of place. not functioning. Do NOT advise disassembly of trigger group unless you are fluent in profanity-
If there IS a problem, pay a gunsmith his pittance to replace the parts.