I used the converter because Build2 disappeared from the platform which worked fine (Google play accepted it) but build 1 only knows SDK 16 (21 is required). So I used the converter. Result = blocks are not displayed. 
No further editing options. Please return the Build2 save option Thank you
Thank you for sharing your experience. We understand the frustration when builds or converters don’t behave as expected.
Regarding your concern:
- Build2 was removed for stability reasons, but the issue you’re facing with minSdk (16 vs 21) is not actually a major blocker.
- There’s already a workaround explained here: Resolving min SDK errors when uploading AABs – Disabling automatic protection in Google Play Console.
- By following that, you can upload your app successfully without needing Build2.
So, this isn’t a serious issue, and your app can still be published without problems. 
That said, we’ll keep improving the build system so that such confusion reduces over time. Thanks for your patience and for bringing this up. 