NLA editor not running multiple actions

Hi. My problem is I cannot get two or more actions to run together in NLA. (I can see this has been discussed before but it was in 2018 and the offered blend file is no longer there) As usual I am a newbie getting in over my head. I purchased a beautiful model with great actions and I am wondering if there could be some deep stuff I am unaware of in the inherited model preventing them playing together or I am just doing something wrong. The image shows what I am doing. Help would be greatly appreciated.
I am running 3.5
Thanks Grouse

Look at the top of the NLA stack for the armature:

Notice that I’ve selected the topmost element on the NLA stack. This element doesn’t have a checkmark; it can’t be disabled as you’ve done. But it still contributes to the final result. I’m showing how it contributes on the right, in the sidebar: it’s set to hold, replace, influence 1.0, which means that it will overwrite all actions beneath it. Those are the default settings. I don’t know what you call this topmost element.

This is how Blender does things by default, so that you can edit an action independently of the NLA. I’m not sure it works very well. It’s certainly confusing (at least, it took me some time to figure out what it was doing.) If you’re trying to assemble some NLA animation and you already have your actions made, you can set the influence of this element to 0.0 in the sidebar shown.

Hi Bandages
I really appreciate the response. I have been over it a dozen times and unfortunately I am still in the same problem, only one action will play. I attach two images showing hopefully what you have instructed. If I select a second action then that disables the first and only plays the last. It seems a strange basic issue to have as I have trawled all the youtube videos. Thanks.

Check out this for a good overview of the NLA, it should help.

What an amazing video - brilliant for a newbie. I can see there is much to learn. I have also fixed my issue with the knowledge from the video - I just needed to put my stitched actions on the same strip. However all the deep stuff is going to be practiced many times too.
Grateful to you both and CGDive!