Moved to For Beginners.

This appears to be a Unity question. You might want to specify what platform you're running on, what your project looks like, how you got into this situation, etc.

2019.2.0b5 ,this happen when import iap

19 minutes ago, ilaya said:

2019.2.0b5 ,this happen when import iap

 

See: https://forum.unity.com/threads/cannot-import-iap-assembly-assets-plugins-unitypurchasing-bin-stores-dll-will-not-be-loaded-due-t.693370/

and

https://forum.unity.com/threads/notice-iap-issues-with-unity-2019.689647/

It's a known issue.

actually I came across all this solution but still it happening

36 minutes ago, ilaya said:

actually I came across all this solution but still it happening

You should reply to that thread letting them know your version number for both Unity and Unity IAP.

You could try rolling back to 2019.1... Is there a reason you're using a BETA build of Unity though for production? Why not try with 2019.2.7f2 maybe? Otherwise there is 2019.1.14f1