https://www.pcgamer.com/pubg-adds-longer-market-restrictions-to-fight-abusive-behaviour-of-the-system/

PUBG players sell cosmetic items for hundreds, sometimes thousands, of dollars on its Steam Community Marketplace. By extending its market restriction policy on bespoke crates, developer PUBG Corp hopes to reduce "abusive behaviour of the market system."

As outlined in this update post, the battle royale's Aviator Crate was released on May 16 and is currently unmarketable on Steam. The developer aims to lift this crate's restrictions on June 13 at 8pm PST / June 14 at 4am BST.