"PENDING TWIC APPROVAL" is an overly broad status all too familiar to many TWIC Card applicants. An overwhelming number of TWIC Card applicants who hear this are no better off than they were before their status inquiry or receipt of their TSA letter.
There are additional steps an applicant can take. If you are one of the many in this "limbo" state with your application you should consider contacting me to discuss your options. Since I specialize in helping TWIC applicants, my experience allows me effectively assist applicants to complete their application and obtain their card without undue delay.