Glitch with Bastok 3-3 Mission

Platform: win10 x64
ISP: twc
Type of Internet Connection: cable
Internet Connection Speed: 100mbs
Date & Time: sept 21 2020
Frequency: 100% of attempts
Character Name: Aliejohan
Race: Hume
World: asura
Main Job: PLD
Support Job: WHM
Area and Coordinates:
Party or Solo: solo and with trusts
NPC Name:
Monster Name: n/a
Steps: In the Bastok 3-3 mission, when opening the Cermet Door with the key, cs isn’t happening and the room is empty. The NPC in Jeuno also isn’t letting me talk to the ambassador.

GMs contacted and they requested I submit a ticket.

If you have any add-ons or tools enabled, disable them to get past the cutscene. several third party programs are known to interfere with various mission cutscenes.

Also as a sanity check, refer to a guide and run through all the steps for the mission exactly to ensure you didn't miss anything. Your comments seem to put some things out of order. So, clarification on a few things:

The cermet key is used to open the door on the first floor which leads to the basement (Note that when you trade the key to the door, you'll get a key item and you won't ever need to get the key again). There is no mission cutscene at this location. In the main basement room, there are three doors. Only one of them is used for your mission, the other two are for the other nation's missions. So make sure you check the right door.

Here is a guide to the mission:
https://ffxiclopedia.fandom.com/wiki/Jeuno_(Mission)
I have never heard of any "glitches" with this quest, so make sure you're doing all the steps correctly and in order. 9 times out of 10 when I see a bug like this, somebody just missed something or didn't talk to an NPC with multiple active quests enough times or something like that.