Trouble Adding Team Member: User Already Exists Error

Hi I am having an issue adding a team member to our organization. It says that "User already exists in account" yet he isn't in the Account Members or Organization Members list. He also does not show up in the existing "Add Existing User" email dropdown. My org URL is https://app.arize.com/organizations/QWNjb3VudE9yZ2FuaXphdGlvbjo4MDc5OnZhUGc Can anyone assist?