Right now battles start if they reach 15 players, or if they reach 10 after 5 minutes it'll start. Less than 10 = deleted. This will get better as the apps launch as more people will have access
~ Fizzer, yesterday at 23:14 CET on Discord
I just tried to join a WZI Battle, but it got stuck at 5/15 and got deleted. I think the limit isn't working. The first ever battle had 8 players, the 2nd battle had 7 players, so it is possible to run with less than 10 players (but only if Fizzer manually starts it). The 10 player limit is too much, the battles just never start. I have not seen a single battle with 10 players yet, but maye one happened while I was away.
With the new update being slowly being rolled out to the mobile devices, we might see an increase in Battle players soon, but I doubt it will increase at all. That is due to the fact that you need to leave your current idle level (why would anyone do that?), to then navigate from your levels menu to the battle menu. As a result of that, you will only find the Battle menu if you are looking for it. And even if you found it, there is a 5/6 chance that there currently is not a battle ongoing, so players will just leave again if they find the menu at all.
The only way to fix this right now, is to lower the limit to less players, otherwise those battles will never starts, and the bugs will never be found.
As someone else suggest in the Discord, make Battles more findable, by adding a Battle icon to the level you are currently playing (same kind as the coin wheel or the ad for +20% income). The Battle icon should pop up when there is a battle waiting for players.