Soul Change Question

[azurerogue]

How does this skill work? According to RMS it's this:

Exchange SP of the target with your SP. With this exchange it's not possible for any of the partners to exceed their Maximum SP. If you use this on a monster, you regain 3% of your SP. You can't use this skill on a monster again that already had Soul Change. You can use this skill in Siege Mode (WoE).

Does this mean that I can't use it if my current SP > target's max and vice versa? That seems impractical. If that is not the case, then why isn't the skill working? I have it now on my professor and I tried to Soul Change a Sniper friend and it simply won't cast. Doesn't say the skill fails, just never does anything, the circle that you use to choose target never even goes away. I used it fine on enemies... but it won't work on other players, and yes he was in my party.

If someone (especially a player with a Professor) could offer any tips, I would really appreciate it. I'll check back later tonight