"Kanske" is an exception! It breaks the V2 rule (verb in second position) and not even sentence adverbials with almost the same meaning are allowed to do that. For example "Du möjligtvis känner henne" is not correct.
The reason why "kanske" works differently is probably because its origin, "kan ske" means "may happen".
Tack för att svara -- I figured this rule, but was wondering if kanske (and by extension ske, sker, skedde) defied this rule? For that matter I also remember being under the impression that handske was pronounced with a hard 'sk' instead of an sj-sound. Have I misunderstood? Tack!