You need mercenary points, ressources and available mercenaries to hire the "normal" mercenaries through the castle.

However, you will need to capture certain mercenary camps to hire slaves, barbarians, teutonic knights and knights templars. Those are available through the obelisk.

Please read this: http://1100ad.com/wiki/Mercenaries

Quote akash1989:

mercenary camp points

... aren't ...

Quote schnitzer90:

mercenary points

Again, if you want to hire any of those:
http://www.1100ad.com/wiki/Mercenaries
... then build an obelisk and hire them through the castle. The only exceptions are...

Quote schnitzer90:

slaves, barbarians, teutonic knights and knights templars. Those are available through the obelisk.

If it still doesn't work, I see three possible reasons:
1. You are someones vassal and owe him/her merc. points.
2. The mercenary unit you want to hire is currently unavailable for you (=> shown grey).
3. It's a bug.

solutions:
1. Get rid of your lord or accept that you don't have merc. points.
2. Wait or use to get your unit.
3. Contact support.

Not too sure about that, but if you really want to get rid of your lord (I'd think about that again, he/she might be mad at you...), I think what you have to do is go to his/her profile and click on a button like...

Quote:

Cancel contract

or

Quote:

Dissolve contract

or

Quote:

Dissolve treaty

I don't know how it really reads though, sorry.

Quote akash1989:

thanks schnitzer90

Any time, you're welcome.

Quote akash1989:

is this a problem of glory points.if yes how to get glory points???

Quote schnitzer90 in another thread:

All the ways to obtain mercenary points that I can think of:
- obelisk
- fountain
- mercenary camp (captured or built by oneself)
- vassal/lord diplomacy
- shared points in guilds

But your description of the problem isn't detailed enough to be sure if this is really a problem of missing mercenary points...