When a new user clicks accept invitation on their email. They will be redirected to create an Atlassian Account followed by creating a Bitbucket Cloud Account.

Once user is logged in to their new Bitbucket Account, user is not able to see / access the repository which they were invited to.

Workaround

Click "Accept my invitation" on the email for the second time after account creation to actually get access to the repository which user was invited into.