Unable to manually generate .h5p file (despite following various forum advice)

Hi All,

I'm teaching a course on moodle and decided I wanted to throw together a little activity instead of having my students go off site. Came across this standard, saw my university had the plugin installed, and decided to give it a go. Ended up with plugin that functions within the Drupal dev environment but seems impossible to pack for actual distribution. It looked like this aspect could be...arcane at times, so I packed the tutorial plugin (greeting card) but to little avail. My most successful packs have at best resulted in a validation error for the library I am uploading itself (e.g. can't find H5P.GreetingCard 1.0 for the tutorial pack). Here is the list of packing methodologies I've tried:

1) 7zip method on windows (as seen elsewhere in forums).

2) Using the cli on windows to generate a zip of the library, and then adding the content folder and h5p file afterwards

3) Using WSL to use the linux zip utility following the switches found posted elsewhere in the forum (zip -r -D -X x.h5p *)

I then swtiched to linux in full and attempted all of the above to the same results. This has to be a problem at the packing stage -- I'm uploading to h5p.com and simply reusing another prepacked h5p works perfectly.  I've attached one attempt at packing the greeting card h5p (done on linux, using the zip command) below. Any advice (especially if I'm just missing something obvious) would be appreciated.

Thanks.