I've tried that, where I buy the necessary equipment or add ons in my load to "unlock" the operations. That doesn't work.
You have to go to the operations screen. Then when you are there it will allow you to press square to purchace new operations for a squad point. It's not based on what you have purchased in your equipment but what operations are active. Even if you have the equipment purchased, if that operation is not active then you cannot work towards its completion.
MUCH AGREED!!!! It is really stupid that the operations are inactive. AHHH!!! Unlocking stuff is half, if not even more fun than just running around shooting people. Activison get your stuff together!!!!!!!!