Hi Alain,
Thank you for the details!
I have checked the configuration, mostly it seems to be all right. Once thing I noticed, that on the Advanced Options -> Exclude/include results panel, you have two categories excluded: https://i.imgur.com/Tq1LIii.png
The missing Pikt-o-norm products might be due to that. If you remove the exclusions, that should resolve that.
The issue with RL74060050 and the other SKU is more interesting. I investigated the product RL74060050 more closely. Everything was set correctly, so I suspected the SKU might not be indexed. I opened the product editor screen, hit the Update button, and it immediately started working.
This usually happens, when the products were either imported by a 3rd party tool, which does not trigger the “save_post” or other actions to notify WordPress about the change, or the product maybe changed via the database, or the hook does not go off after saving. If you use any 3d party editing tools, that might explain that.
I suspect, if you open the other product RL814015075 and save it, it will appear in the results.
If you notice an increasing number missing products, or importing bulk number of products, I recommend fully recreating the index, that should do the trick.