Paul, No major difference in 7.65 & 9mm mags except the 9mm had a slightly stronger mag spring. The HO is activated when the round follower button of the right side of mag pushes it up when mag follower is at the top. quite often, this button is worn or the right grip interfers with it's movement. TH

After cycling the action and looking at the magazine it appears that the mag hold open is worn down. I do have several photos but could not figure out how to post them?

There's a sticky in the New Collectors' section explaining how to do it. It is preferred that you post copies on this site, as hosting sites and the pics on them tend to come and go. It's nice to have the pics a post is talking about show up no matter how far in the future someone reads it.

IIRC, the hold-open should be numbered to the gun. Get a replacement for shooting, have the original part rehabilitated if it's numbered.