Rocket League has just received its latest update, V1.61, and while it does introduce new hotfixes, content, and features, what makes it and/or breaks it is the fact that Psyonix opted to disable Crate opening for Belgian and Dutch players.
Rocket League Belgium Crates are, then, no longer accessible at all due to "government regulations", and Rocket League patch notes V1.61 were mostly overshadowed by this change.
Rocket League Players in Belgium can no longer open Crates?
Due to various reasons, Psyonix did not opt into attempting to rework Rocket League's Crates - lootboxes in all but names - to try and comply with laws enacted in Belgium and Netherlands, and have instead chosen to disable the feature entirely in said countries. Effective as of V1.61, players from either of these countries can no longer open Crates with Keys. Related is that everyone else can now access Crate item drop rates in-game, on the Crate Preview screen.