A D6 suspension is typically applied to people who have unresolved tickets and/or fines. The suspension will remain indefinitely until the underlying reason(s) are dealt with. Go to the clerk of the county court where you reside. They can pull up your driving record and tell you exactly why you have a D6 and what you need to do to remove it.
The D-6 will last until you address the reason it was entered. For example, if you failed to pay a ticket or show up for a court date, the Judge will typically enter the D-6. Usually, you can pay a late and/or re-set fee and get the D-6 cleared. A more serious matter will require you file a motion with the Judge to have the D-6 removed.
As counsel has indicated, you must determine where the D6 originated. Hopefully it is in the county in which you reside. Your driving record, obtained by any county clerk's office in the state of Florida, will show the suspension and the ticket numbers on the far right will determine the outstanding tickets which must be paid. Also, if you have been ordered to do something in regard to an offense, and you have not done it, for example,if you had a conviction for a dui or a wet reckless and you did not complete the Alcohol Safety and Education Course, it will indeed remain forever, and may preclude you from receiving a Driver's License in another state.
Good luck and have patience.