As the title says.
I’m trying to implement codeless IAP with Google Play Services… did this 1000 times but not codeless… and I’m getting this error:
2019/12/03 22:02:49.970 10551 10567 Error Unity Purchase failed because Purchasing was not initialized correctly
So now I’m wondering… which Package should I install? From the Package Manager v2.0.6? or From the Asset Store v1.23.1?
And Why you keep 2 separate packages? 
You need both packages, we are working to make it a Package Manager package only in a future release. There are many reasons why it might not initialize, but if you have done this many times before, what is different this time? Make sure you follow the steps here, and you must use a tester account, browse to the opt in link on the device which will then send you to Google Play to download the game. You can’t just install the APK directly the first time you install, but subsequently you can. Unity - Manual: Configuring for Google Play Store