HELP! for .22 mag Rossi pump

[Old Ford47]

Hi,
I have a Rossi .22 pump, in almost new condition.
The problem is it will not lift a round into the chamber.
I have a Rossi .22 lr., I have had it for forty years without a single failure.
I have compared interior parts, and can see no difference, except longer dimensions for the .22 mag.
I have dome many repairs to many different guns through the years, but this one stumps me.
Any suggestions will be appreciated.
I cannot find a Canadian Rossi repair depot either.
Fred

 

[Can-down]

Location Snap Shot used to be the Rossi parts source but when I tried to get some basic screws a few years back they were unable to source them.....

 

[BCRider]

If you cycle the magnum without ammo does the round carrier snap up and down like it should? If it does then check that your ammo is not too long so the nose of the bullet is still into the magazine tube opening. You may simply have some fouling or other debris in the cartridge hole of the carrier that is blocking the round from fully seating. The other thing is look down and see if the cartridge interrupter is holding back the next round so the head of the round isn't similarly blocking the carrier from rising up.

This is pretty basic stuff and I sort of assume you've done this already. But just in case......