Well, you can try what I suggested: Load the autosave (which should put you where you first started the level) and try again. Don't try the door code; just go by the door to trigger the task to find the scientist, then go to the scientist and see if you hear the message this time.
If that doesn't work, click the link I posted (in my earlier post) for ZRP to get an explanation of what it is. Click the downloads link to get it if you want to use it. To install it, you would extract the gamedata folder from the ZRP archive (using 7-Zip is easiest; it's free if you don't have it), copy (drag-n-drop) that gamedata folder to your SoC installation folder, and then edit <SoC installation folder>\fsgame.ltx with Notepad or other editor and change any
false to
true on the second line of that file (so that there are two
trues on that line) and save.
There are debug tools you can use (and I'll walk you through them) to give yourself the info_portion to play the PDA sound and to activate the door.
ZRP also has the ability to remove a door and then restore the door, or you can reset the door's logic, although the code lock is a separate logic and it is probably what is not working properly. We can try things that are a little complicated, but I can post instructions here for you to follow like a recipe, so that you can enable the debugging support and install the special scripts that allow us to fix this problem.
ZRP has
a support thread at
the GSC forum's SoC subforum's Mod Discussion section, and you can visit
the STALKER subreddit and examine the sidebar for more details about ZRP.