Update (May 10 - 6:30PM PDT): We are currently investigating issues causing tanks to remain locked after this news announcement.
Tankers! Clan Wars participants!
Tank locking has been disabled; we apologize for any confusion. This feature was not intended to be activated on the NA cluster.
Even if your tanks show that they are locked, they can still be used on the Global Map as normal. The locked display is simply an issue with the game client that will be resolved shortly.
Thank you for your patience.