Global not going in effect????

[Master Shake]

In a long MP game. Had Gift of Health up. Had is replaced by other globals, to the point where the game eventually had 6 globals up. Several have been dispeled, and only 3 Globals remain.

I tried to cast Gift of Health again, but got a message that it was overpowered by existing spells. No other player got GoH up that turn. Why did my spell not go up??