invalid user: ‘vagrant:vagrant’ fix

This means you don't have such user in guest OS. Check also `override.ssh.username` in machine Vagrantfile

Sulu /admin/translations/sulu.en.json?v=develop error fix

Be sure you haven't deleted sulu.en.json in project web/admin, and there anything will not be deleted (for example as Vagrant's Rsync do that). After this restore translations with php bin/console sulu:translate:export .

Vagrant SSH Permission denied (publickey,gssapi-keyex,gssapi-with-mic) fix

If you receive error "Permission denied (publickey,gssapi-keyex,gssapi-with-mic)" or "No more authentication methods to try." in verbose mode on connect via SSH to guest, also noticed that works when you disable provision script, this means your script contains error and so other Vagrant scripts cannot execute for correct SSH working.

Solution is to fix your provision script.