Error: incompatible ruleset when changing configuration

If I try to change ruleset in configuration to the one with more player attributes I get error:

“Error! Cannot edit the matchmaking configuration. Reason: A matchmaker configuration may not be updated as requested due to an incompatible rule set change. If this new rule set is desired then a new matchmaker configuration must be created. Error = A new attribute was introduced.”

Can you, please, explain the reasons behind this requirement?

@Ludd, thanks for trying out FlexMatch and GameLift!

If you add an attribute, players currently in the matchmaking queue associated with the current matchmaking configuration will not have that attribute and will no longer be able to match. As such, you need to create a new matchmaking configuration containing the rule set with the new attribute and route players to that new configuration.