I disagree. "Experiencing outages" means something more than any of the other phrases you used. It's also more professional. "are down" doesn't tell you whethe

I disagree. "Experiencing outages" means something more than any of the other phrases you used. It's also more professional. "are down" doesn't tell you whether it's intentional or not (whereas "outages" is a word that people don't use for expected downtime). "are having problems" and "are not working" don't even tell you anything about the symptoms. But "experiencing outages" means the service is partially or completely interrupted, and that it wasn't expected downtime.