I made a SSH key but adding this key to bitbucket says it is an invalid key

[MDAUTOMATISERING]

After trying to push in Sourcetree I get errors

git -c diff.mnemonicprefix=false -c core.quotepath=false --no-optional-locks push -v --tags origin master:master
remote: Bitbucket Cloud recently stopped supporting account passwords for Git authentication.
remote: See our community post for more details: https://atlassian.community/t5/x/x/ba-p/1948231
remote: App passwords are recommended for most use cases and can be created in your Personal settings:
remote: https://bitbucket.org/account/settings/app-passwords/
fatal: Authentication failed for 'https://bitbucket.org/MDAUTOMATISERING/a.git'

[Ben]

G'day!

The error you have mentioned indicates that SourceTree is still trying to use HTTPS for authentication, rather than SSH. This is why you are receiving an error related to App Passwords.

Please see the following article for Sourcetree if you would like to continue using App Password:
https://community.atlassian.com/t5/Sourcetree-articles/Bug-Fix-Sourcetree-for-Windows-authentication-error-when/ba-p/1965968

If you would like to make use of SSH in Sourcetree, there is an article here which explains the process for Sourcetree as well:
https://support.atlassian.com/bitbucket-cloud/docs/set-up-an-ssh-key/ 

There is a chance your GIT config still has old references to HTTPS present, I would suggest clearing these and following the articles above.

Hope this helps.

Cheers!

- Ben (Bitbucket Cloud Support)