Per the Official Code of Georgia Annotated (O.C.G.A.) a challenge can be made to a voter's eligibility to vote.

Three challenges were made to the Forsyth County Board of Registrations & Elections.  On December 22, 2020 the Forsyth County Board of Registrations & Elections held a Special Called Board Meeting to hear the challenges.  Two of the challenges were denied and the Board found probable cause for the challenge of eligibility to vote of 5,000+ voters filed by the third challenger.
Letters were issued to all electors on the Challenged List.  In order to satisfy your challenged status and you reside at the Forsyth County address on the letter, please follow the steps outlined in the letter. 
If you received the letter challenging your eligibility to vote in the upcoming election and you no longer reside in Forsyth County, Georgia, please complete and sign a request to have your name removed from the voter rolls. 

Challenge Grounds
List of Challenged Voters. 12.22.2020 Board Meeting