Swapping from my pve set to pvp set, or pvp to pve set causes the set bonus to not apply. Removing all my gear or relogging is the only way to reset it.
EDIT: Figured it out... Cloak of Consumption and 2pc are interacting in some fucked up way. If you are missing +23 SP just redo your cloak instead of relog. Or perhaps some other item you have with +23 SP.
Are you using 3 piece t2 and 2 piece r10 for your pvp set? I can make pictures too to prove you're wrong and in my situation changing the cloak isnt fixing it.