4v4 Custom Matches were missed in the PvP update and still require level 60 to start. You can switch to lower level classes once inside, however to initiate the custom match you need all players to be level 60 or higher. This doesn't coincide with the new PvP changes, which only require level 30.

When submitting a bug report, please use the below template and thoroughly fill out the necessary information.

Time: 11:48 AM
Frequency: Always
World name: Leviathan
Character name: Koltik Morrel
Retainer name: N/A
NPC name: N/A
Monster name: N/A
Class/Level: 32 Scholar
Party or solo: Party
In-game time: N/A
Area and coordinates: The Feast
Housing: N/A
Steps:
1. Put two parties of four together on the same server.
2. Have any amount of players on classes higher than lvl 30, but under level 60, in the parties.
3. Try to join a custom match.
4. Custom match gives an error saying that one or more party members do not meet requirements for the duty.
5. Have the players under level 60 swap to a level 60+ job
6. Error disappears and customs now work.