Problem: "Someone has already added that key as an access key to a repository."

[holmes88]

i am having the same problem 

[Nic Brough -Adaptavist-]

Welcome to the Atlassian Community!

This happens when you have tried to use a key for an account with a different account.

The "fix" is to stop sharing keys (you shouldn't be doing that in general, it's not just Bitbucket).  The second account should generate and add its own key to the repository.