[2019] PrimalGameData_BP

Just a few things off the top of my head:
1) make sure your engram is set to a level higher than 0 and requires at least 1 engram point to learn. (I've seen oddities like this with anything less) and that there is a crafting cost to them (1 wood or thatch is what I usually do for testing)
2) Make sure not of your engram items have any of the "deprecate" flags enabled.
3) Make sure any assets referenced are actually in your mod folder. not all of the assets in the devkit are actually packaged in the base game.
If all else fails you can try replicating what I do in my tutorials, having a visual example might help spot anything that was maybe forgotten. Episode 3 is where I actually create a first mod that includes the stuff you are working with now: https://www.youtube.com/playlist?list=PL2o1TY9xh_JsmbgQfSCydfT-7OSdvxsVR

Potentially. If you know the assets are in the game you generally don't have to copy them over, but if you aren't sure then you should probably use copies in your mod folder to be safe.
As for the deprecate flag if you go into the defaults of your primalitem and search "Deprecate" you should get one or tool boolean parameters make sure they are not set to true.
You can also compare your mod files that are downloaded. if you go into the directory that gets downloaded from steam you can check for yourself to see what files were uploaded. If something is missing then you have a potential starting place to find out what is going wrong.

It's possible that the version gap could be causing issues for you. Might want to hold off until the devkit update makes its way to the epic launcher and then confirm if the issue continues to be a problem.
Generally though making children of blueprints is the safer way to do things.