In late February 2017, the Virginia Department of Elections removed 1,592 inactive voters from the City of Manassas voter registration roll and 196 inactive voters from the City of Manassas Park voter registration roll. You might want to check if your name is on one of those lists.
Note that both lists of purged voters are organized by numbered voting precincts, and for the City of Manassas those numbers reflect the new (starting in 2017) voting precinct boundaries, not the precinct boundaries that applied in recent years. The precinct codes for each city are as follows:
PCT Manassas Polling Location
0001 Dean Elementary School
0002 Weems Elementary School
0003 Metz Middle School
0004 Haydon Elementary School
0005 Balwin Elementary School
0006 Round Elementary School
PCT Manassas Park Polling Location
0001 Manassas Park High School
0002 Costello Park Community Center
0003 Manassas Park City Hall
Reportedly, a voter registration is purged only after a voter fails to respond to mailers sent by the State Board of Elections concerning ones correct address and then fails to vote in two Federal Election Cycles following that mailer.
The best and easiest way to verify that your voter registration is still valid is to review your voter record at the Virginia Department of Elections voter portal, after entering your name, date of birth, locality, and last four digits of your social security number.