The Resident Evil 4 keycard objective will see you trying to rescue Ashley in a dark lab, flipping power between sections and solving door code puzzles. Get through it all and you'll activate and upgrade a keycard from Level 1 to Level 3 and eventually open the door keeping Ashley prisoner.
You'll have to deal with some Regenerador monsters for the first time here in the Resident Evil 4 Remake, at a point where you can't initially kill them. So avoid them as best you can when they first appear, and remember that they won't follow you back to where the Merchant is if you need a breather.
So here's a walkthrough to help you get the keycard in Resident Evil 4 and upgrade it to level 3.
