Ruger 22/45 chambering question

I am going over my (deceased) husbands guns. Found a Ruger 22/45 with no magazine in it. Finally found a magazine that(I believe) fits it, put 22lr bullets in it but cannot get it to fire. I do not believe any bullet is in the chamber and cannot pull any bolt back to load the first shell. What am I doing incorrectly?
I have pictures to attach but cannot see how to attach here.

Thank you.

There have been three 22/45 generations, the MkII, MkIII and MkIV. Their magazines are not interchangeable.

He also had some Glocks, which the magazines are quite a bit thicker. This is his only Ruger. So if it fits it and snaps nicely, is there a chance it is not the correct magazine? This magazine is so narrow it does not seem to fit any of his other guns.

The bolt is pretty hard to pull back on an uncocked gun. Grab the ears at the back of the bolt and pull hard. Below is a 22/45 with magazines and the bolt pulled back, also is a link to the instruction manual for that gun.

https://ruger-docs.s3.amazonaws.com/_manuals/markII.pdf

I recommend you take both the Ruger pistol and the magazine you have for it to a good gun shop and have them see what you have and if the magazine is the correct one.

The instruction manual showed me how to pull back the bolt(I tried previously but not hard enough). Round chambered, gun has been fired. Thank you.