mdmellott hit the nail on the head with " released the catches " , they're VERY tricky , tough to get a good visual on it and have very little feedback telling you they are IN FACT released , cause when you "get it " you'll be surprised at relative ease of pulling them out.
Big Tip :Must be fully SEATED to enable catch to release easily , like a vertical pull OR NOT seated will be a bidtch trying to use the small flat screw driver needed. And IF your PULLING relay while leveraging screwdriver , the catch is "caught" and WILL NOT release ,ya