summoning does strange!

I have summond till i was summon lvl 11 and now he says:

you can summon 0 npc's

wth is that all about.
i cant get it fixed.
could somone help me out with this one plz i like the summoning skill.

BTW: my whole server needs a make over its full with bugs.

ty for reading and i hope to get a respond soon.