sounds like the PSE pump under the rear seat. a easy way to check if the pump is working is to swap the left and right door hose and see if your right doow unlock while left remain locked. If it does, it means your pump have failed. If no difference, it means your pump is working and the hose is leaking....

I would also disconnect the pump to reset it. Re-connect power connection after 1 minute and see if there are any difference.