Since the tenant has failed to pay their rent, then you can start the process of eviction. You can get a Pay or Quit notice in which they have a certain amount of time to pay or move.
If you dont want to get that aggressive, call the tenant and tell them you still have not received their rent. Ask if there is something going on keeping them from paying like job loss. If they dont give you a reason, then you can inform them that they have until (date) to pay or you will start the eviction process. This is normally enough to get them to pay or inform you that they cannot pay you the rent.
