When i try to upload my web part to App Catalog in my on-premise SP16 server Valid app package is NO?
How to solve this problem? Not yet available for On-premise?
It is not yet available for 2016 On Premises. It will be available via Feature Packs later this year for On Prem.
Its coming to SP 2016 as part of Feature pack 2.
Currently its only available for SharePoint online.