Not related to thaumcraft. just TRY AGAIN and AGAIN and AGAIN until it works, do NOT change the Modpack in an attempt to “fix” it, it will just randomly WORK without YOU doing ANYTHING AT ALL.
Do not see this as an Issue that can be fixed by changing the Mod List, see this as an Issue of LITERAL GAMBLING UNTIL YOU WIN, because THAT is the thing happening to you right now, LITERAL GAMBLING. The Issue will sometimes happen and there is nothing you can do about it, just ignore it and try loading the Game again and it will likely work.
Again, just try again, try again, try again until it works, that is the TRUE AND PROVEN solution that DEFINITELY WORKS, no sarcasm, no irony, no kidding, just BRUTE FORCE.