/zh claim command just gives me message 'You have reached your claim limit' regardless of the settings in config.yml

Make sure that the group names defined in the config match group names defined in your permission plugin.

If you have set something like this for a specific player who should be able to claim 10 horses :

Groups:

    vip:

        color: <red>

        color-bypass: false

        claims-limit: 10

Then this player should belong to the permission group "vip" defined with PermissionBukkit/PermissionEx/...