• Amazon added a new feature to its Amazon Seller App to help merchants who sell in more than one region. The Single Sign-on feature allows sellers to access all of their marketplaces with one credential.
  • However, sellers must have their cross-regional accounts linked to use the feature.
  • Single sign-on (SSO) is launched on the Amazon Seller App. If you have cross-regional accounts, use SSO to reach all of your marketplaces and linked accounts with any set of account credentials. Then you can use the marketplace switcher that is located at the left navigation menu to alternate between your marketplaces.
  • SSO on mobile is already in effect if you have linked your accounts. If your accounts are not linked, visit linking accounts here and follow the instructions.

source:

https://sellercentral.amazon.com/forums/t/single-sign-on-sso-is-launched-on-the-amazon-seller-app/492971