For any other reason, then you will have to go through the whole validation process again, including the physical appointment
at the FSDO (or if available, with an FAA representative outside US).
If you hold a former TT or PP license, or a JAR-FCL license (eg : F-LPA00123456), then you will have to contact first the DGAC to have it
converted into a Part-FCL license (eg : FRA.FCL.PA00123456).
During this process, the FAA will contact the DGAC to verify the authenticity of your license.
Since June 2016, this processus was simplified through the SIGEBEL server. This requires that you connect on your personal SIGEBEL access
to authorize the FAA to access your data.
Information here about the process through SIGEBEL.
You will need to know you height in inches and your weight in pounds.
If you are not familiar with these units, this converter from cm/kg will help you: