Squeeze harder??
The old Contenders can be very, very STIFF. And what I mean by stiff is that some people lack the handstrength to open it, even when the gun is clean and in perfect mechanical condition.
Can't say about the gun you have, maybe its broken, maybe its just sat so long oil turned to glue, Rusted shut?? case rupture freezing the action??? Lots of things possible, can't make a good guess without more information, sorry.
First, verify its not loaded with a live round. Rod down the barrel CAREFULLY, measure and mark where it stops. Compare with barrel length and this will tell you if there's a bullet in there...
Remove the rubber furniture, and give it a few days soak in a good penetrating oil. Then see if you can open it....
FYI, the way the old Contenders work, once the hammer is off the sear (fired or lowered by hand) they will NOT reset until AFTER the action is opened. That's just the way they were made.
I have seen Contenders where it literally took both hands squeezine on the triggerguard to get them open. The pair I have are stiff, but not nearly that bad. I can do it one handed. My wife however, cannot....
When T/C replaced the Contender with the G2 Contender, they corrected the "flaws". The G2 opens easily and the hammer will reset on the sear without needing the action to have been opened.
Soak it for a while, then squeeze like hell, that MAY be all that's needed. If not, then tis gunsmith time....
Good Luck!