If your mail was returned to sender, this means that USPS attempted delivery at the original address but was unsuccessful. This could be for a variety of reasons such as an incomplete address, inability to access to the premises, or a recipient no longer at that location.
In these cases, we recommend confirming this address with the intended recipient and submitting a new request to have it printed and mailed. Lob does not re-initiate mailers (there is currently no way of re-initiating an existing request in Lob).