I decided to start my first character in hardcore just to see how far I could get. I died for the first time a little bit after choosing my faction in the campaign. I continued to play that character on softcore. I now went and made an alt on softcore and the NPCs to choose my faction did not show up in Keepers Camp. I believe this is because that even though my first character is NOW a softcore character, he originally started and chose the faction as a hardcore character. Even though now both these characters share a stash my alt cannot choose it’s faction at the first town.
This seems like a bug since the only info on this is that a character simply needs to share a stash with the character that chose a faction in order to join a faction earlier on an alt.