When can you not use Counterspell?

[MarkVIIIMarc]

Are there any quickened or subtle meta magic combos which you don't get a reaction to cast Counterspell against?

[Zanthy1]

Are there any quickened or subtle meta magic combos which you don't get a reaction to cast Counterspell against?

I believe that most DMs will say that you cannot counterspell if you cannot see the spell being cast, such as through the subtle metamagic. In fact, thats one of the primary uses from my understanding of the subtle spell, in addition to the stealth bonus.

However Quickened spells I would say are still counterable, but if they were quickening a spell and casting another spell you wouldn't be able to do both obviously.

[Kane0]

When you are beyond 60'
When you cannot see the spell being cast
When you are unable to take reactions, such as being surprised or incapacitated

[Dalebert]

Subtle spell is obviously great for avoiding getting CSed. I've heard Distant can also be nice. Be over 60 ft from the caster. Use Distant as needed to make up the range. Even Counterspell the caster by extending the range and he can't CS you back because you're out of range.

Doesn't work in tight spaces which are fairly common. That's when you'd want Subtle.