Since Wednesday 13 Sep 2017 we're having intermittent issues to clone, pull and push due to ssh authentication issues. The Bitbucket status page doesn't mention any issues on your side, but I'm pretty sure it is.
We get the following error a lot but not every time:
Connection to bitbucket.org closed by remote host. fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.