First you MUST have the contact phone number in order to look any further. Once you have this you can begin using the platform to see exactly what is happening with that number. 

Here are a few questions to ask: 

• Contacts can often miss out on receiving text if they do not meet the criteria of target lists and recipient types being used to send the messages. Send them an individual message to test their device's ability to receive a texts from the system.

• Contacts occasionally forget that they've opted-out or inadvertently reply stop and accidentally opt-out. They will need to opt back in to receive texts. Have them text-2-join your keyword.

• Contacts can also change carriers. When they do this, the system information needs to be updated so that the carrier is correct. Perform a carrier look-up on the number from the contact details page. Does the mobile carrier information change?

• Additionally, changing carriers can also include a change in permissions that the contacts are not aware of. This is called a marketing block and carriers are increasing their tendency to add the restriction to new sign-ups and upgraded plans. Unfortunately, there is nothing the system can do to help when this is the cause. The contact will need to reach out to their cellular service provider to investigate and resolve the issue.  

• Rejected, Failed, and Invalid Destination status are typical signs of a marketing block.