Progress in the Uninvited mission of 007 First Light stalls until you reach the CCTV Room, and that door only opens with a specific card. You actually need two cards to pull this off. One gets you into the office area, and the second unlocks the security door itself.
Get the Museum Key Card near the Aerospace Room
The Museum Key Card comes first, and you grab it during the party section before you ever reach the security door. It opens the doors leading into the office area where the second card is kept.
Step 1: Head toward the Aerospace Room and look for the guest wearing a blue outfit. Stay close enough to hear them talk, since they mention carrying a card.
Step 2: Create a loud distraction to pull their attention away. While they react to the noise, move in and pickpocket the Museum Key Card off them.
Step 3: Take the card to the first set of locked doors and use it. This opens the way into the office area where the CCTV Key Card is hidden.
Take the CCTV Key Card from the glass office
Inside the office area, guards patrol and cameras watch the floor, so the card sitting in plain sight still takes some care to reach.
Step 1: Move through the office while hugging the walls. Keep out of camera sightlines and stay behind the guards as they walk their routes.
Step 2: Look toward the back of the room for the glass office. The CCTV Key Card is resting on the desk inside it.
Step 3: Knock out the guard standing near the desk before you grab the card. Taking him down first stops him from raising an alarm while you take the card.
Unlock the CCTV door by the pool table
With the second card in hand, the security door becomes accessible from the main room.
Step 1: Go to the main room that holds the pool table and the games. Find the door clearly marked CCTV.
Step 2: Clear your path to the door. You can sneak past the guards or take them on directly, but make sure nobody is chasing you when you reach it.
Step 3: Use the CCTV Key Card on the door to unlock it. Once it opens, you step inside the CCTV Room and continue the next part of the mission.
Knowing the door opened and let you through is the confirmation that everything worked. If the security door stays locked, you are most likely still holding only the Museum Key Card, so return to the glass office at the back of the office area and collect the CCTV Key Card off the desk before heading back to the room with the pool table.