Why can’t I switch my X account for the repost campaign?

First, access the page below. Next, locate the button with your account name on the upper-right corner of the screen, then tap it to log out.
https://api.twitter.com/oauth/authenticate
*Accessing may cause the page to display an error message, but you will have no problem logging out.

Afterwards, access the campaign page via the notice in the app. By tapping the “Switch Account (アカウントを切り替える)” button on that page, you will be able to change which account is linked to the campaign.