First I checked the base sector setup and found that Team 1's starting_territory_team marker was set to 'World'. I set it to Player 1 (you should do this too), and I thought I'd cracked it... but no.
I wracked my brains, saved, exported, opened CoH2, couldn't find it, saved, exported again, to no avail. Then I wondered if your filename Interactivity(3x3 732x732)Ready.sgb wasn't a bit long. In desperation I saved it simply as 'Ready.sgb', then exported that...
...and it worked! Either the name was too long, or it had the wrong characters in it, but saving it as Ready.sgb made it work.
You should be good to go now. PS, I like the little picnic scene, looks like everybody left in a hurry.
Just to confir, is creating a Costum Game in Online & Skirmish, and lock for the map on the Select Map?
Yes, this is right. I don't know what's going wrong. Perhaps the thing to do is upload the SGA to a file sharing site, then post a link to it here, so somebody can open it in WB and look at it.
In Worldbuilder, go to file -> Export Package. That'll make it playable on your copy of CoH2, but nobody else's. You can play custom skirmishes on it and make sure everything works.
To upload it to Steam, go to Workshop in the CoH2 menu screen, select your map and click 'Publish'. If you want to change it, just make changes in Worldbuilder, then export and publish it again - as long as the filename hasn't changed, it'll just update the old version.
Here's my second go at an MP map. It's a bit more ambitious, with lots of destroyed buildings. Fiddling about with all the structural damage was exhausting.
Since I got so many helpful tips from reading these forums, I thought it was only right that I register and submit my maps here. This is my first attempt, let me know what you think.