'Idle complete' means you have no games with card drops remaining. See your badge page for those words "card drops remaining".

Steam only gives you half a set per badge.

It's because a tech implemented the 2 hour refund system and customer services are never trained well.

https://psteamcommunity.yuanyoumao.com/groups/idlemastery/discussions/0/133257636766989675/

It's very likely permanent because they've decided you got a refund, that's a one way street.

You could try support but my hunch is they won't know what you're talking about and they'll just spout some annoying rubbish so as they can close the ticket.

You have 1 game, it's pretty pointless installing it. Otherwise see pinned threads.
IdleMasterExtended is on github:
https://github.com/JonasNilson/idle_master_extended/releases

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https://psteamcommunity.yuanyoumao.com/groups/idlemastery/discussions/0/3049483103525683298/#c3049483103525806556

That's exactly how trading cards work, free games don't drop cards and paid games only drop half a set. There's no point in buying games just for the cards, you might as well just buy the cards instead.

Link fixed

Oops, link fixed.

Don't worry about it, it's never happened before so far as we know.