For the people that sometimes have problems with subclass...
First requirments to take a subclass.
--> Your main class, or any other sub has to be lv75 or over this level.
Subclass, can't add? Take a Look. This is why:
1 - If you're any mage like SpS, Sorc or SH. You're not able to add any other.
Example: You're SH and you want to add Sorc.
If you're an archer like, PR / SR / HE, you won't be able to add any other.
Example: I am a HE, and I want to add SR.
I am an Elven elder, Shillien saint, prophet. You're not able to add any other.
Example: I am a Shillien saint, I can't be prophet.
And so on.. Classes with the same "Type" of skills, you won't be able to add any of the others.
2 - It was always like this: If you have an Elf class, (example, PW/TK etc), you won't be able to add ANY dark elf class(example, PR / SK) Or, if you're dark elf, you won't be able to add Elf classes (obvious). It's just like this, it always was since you are able to subclass in lineage.
And I saw many people asking: I am a BladeDancer (Dark elf class), where can I add SwordSinger (elf class) Sub-class? Or I'm a Sws (elf), where can I add my BD(dark elf) sub? Well, read above here. To solve this problem you've got to make another sub-class first. Like, Warcryer, or any other Non elf/dark elf class ( Depends on what class you are).
3 - I am a Silver ranger, my subclass is necromancer, but I can't add Phantom Ranger or Hawkeye sub?
3.1 - Check if your necromancer subclass is lvl 75 or above.
3.2 - Check if you're not on your main class Silver ranger, so be sure you're Necro. (Why I have to be necro? -> see above)
4 - I am Necromancer, main class. And my subclass is phantom summoner, I pressed the wrong button. But, I can't "cancel the current sub-class etc etc" . So I really have to level my PS to level 75 to cancel my subclass and take another?
Answer: No, you just have to change to necromancer again, and press "cancel current sub etc etc". Why? Because that class is level 75 and above.
5 - Well Now, you can take any sub-class you want, but not (Read above, why). But there are only 2 exceptions, and that is Dominator (Overlord) subclass and Maestro subclass(warsmith). Why? Because NcSoft made it that way :p