A couple things I can think of:
- user credentials are wrong
- url to server is wrong
- user does not have access to the deployment repository
- user does not have access to the specific repository target
- artifact is already deployed with that version if it is a release (not -SNAPSHOT version)
- the repository is not suitable for deployment of the respective artifact (e.g. release repo for snapshot version, proxy repo or group instead of a hosted repository)
Check those and if you still run into trouble provide more details here.