Queue triggers do not work for 2nd item and after.
A workaround is to decrease the interval with which the queue items are checked.
By default it is checked every 30 min, thus it takes up to 30 min for the queue items to be picked up.
The interval can be changed by editing the "ProcessActivationSchedule" parameter.
Please refer to the following documents for details.
Please be aware that the queue triggers has to be created again after the configuration is changed and IIS is rebooted.