How the hell every other topic on the forums are game breaking bugs... did you actually test the game before release?
The AI (Sigurd and Basim) are not reacting to the doors of the longhouse. They are agroing the enemies but not proceeding with the quest

can't progress or continue the quest a brewing rebellion, the part reach Buckingham's longhouse can't be done due to sigurd being bugged and not doing anything just standing still and not helping with the door, just hade to reset the game 4hrs yesterday due to another bug but it seems to reset this quest i need to reset the whole game, and with 38hrs put into it i don't really think i can do it, any help would be appreciated

@ubiexcellent i have a video of it, how can i send it to you?

@frostik-rus i just found them in the middle of Buckingham but they are just standing not following me or reacting to anything

@blackwidowsport i also have this problem, did you find a solution

Just reload the quicksave and it is fixed

@ashtg133 I am having the same issue on my xbox one. Companions are right next to door, but not helping me force the door open when I push the button. I've tried reloading older saves, but am still having this issue! A real shame as I'd like to continue the game.

Same here on pc

Same here, tried to reload an older save, but it didn't worked.

also having the same problem, Sigurd and Basim refuse to help me open the door after I've killed everyone in Buckingham

edit: on PC

also having this same issue on PC, reloading older saves isn't helping

Guys, im starting over, I'min England already. Let you know if I get the door open in Buckingham. Pray to Odin Sigurd will help.

I found a sort of fix.. Use your Horn (the G button that summons raid) this forces that assasin guy to come by your side.

After go back to the same spot you released the prisoners with the executioner and run down the way they faced. They refused to run around it seems..

There is a glitch on the mission Brewing Rebellion where you cannot get into Buckingham's longhouse due to Sigurd being glitched and just stands still. This stops me from progressing the main story.

@dingusbopper me too, I accidentally broke into the side door and killed them instead of the door and he is free but glitched

@halaloya Yeah... same. But they are attacking enemy if near them and then they go into standby state... I guess AI is broken on that mission

@halaloya Same problem here. Tried everything. Hoping for swift action from Ubi

@ubiexcellent can you please respond and let us know that this issue is under investigation? We need some relief that this bug is known to you

After starting again with a different account snuck into buckingham and opened the doors of the longhouse with the help from Basim. Make sure your level is high enough for the next part. Cheers

Another one here who is stuck with Sigurd and Basim doing nothing. Tried reloading, fast travelling, unmarking the quest, using the horn- nothing has worked.