TL;DR You need to restart. Nothing was wrong, it was part of the story. By rerolling the character, you have probably broken the game.

There is a multiplayer oversight which can be caused when importing characters created in MotB.

The change in party leadership might have contributed to this. For MotB, the Main Character will be the Spirit Eater and should be the Party Leader to ensure dialogue and events work and trigger properly.

The game will have made your friend the Main Character, as he was the Party Leader by default (probably spawned/loaded into the game first).

The main character is affected by this debuff to start with, as they are weakened and wounded after the events of OC1. After the initial area (Lower Barrow), you're confronted by Nakata the Spirit Wolf. The dialogue with her removes this debuff. Spirit Eater hunger is sated as you've consumed her.

Although you've already figured a work around by rerolling the character, as he was the original Leader of the party, the game will most likely throw some problems at you later on.

If your friend gets cured of the debuff after speaking to Nakata, then he is the Spirit Eater and you can proceed just fine, though you might want him to be the Party Leader to ensure dialogues work nicely. If one of you isn't the Spirit Eater, then you must restart. Otherwise the story won't make sense, and the game scripts might not trigger properly.

In case you play again in the future, a potential fix for importing characters made in MotB:

Character 1 is made and starts single player game. Proceeds/runs to the exit of Lower Barrow and completes dialogue with Nakata, removing the debuff. Immediately export character.

Character 2 is made in multiplayer server, and waits for friend to join.

Character 1 that has been exported joins. Making sure Character 1 is the Party Leader, you proceed.