Can't Sideload for the LIFE of me .s9pk package file invalid

I was able to get an open Source app called Change Detection running on http://mystart9.local:5000 port but for the life of me I spent over 10 hours now working with Grok to be able to upload / sideload the .s9pk package file but it always says Invalid Package File.

I don’t have any more ideas other than to write here.

Did you follow this guide?
https://docs.start9.com/0.3.5.x/developer-docs/packaging

Yep, with grok followed

Are you getting errors anywhere? If so, during what command? Maybe you can post the output of your make command. What OS are you building on?