What we diagnose and fix
Inverter failures (string inverters typically last 10-15 years, microinverters longer — but both fail). Monitoring system dropouts (your app says "no production" but the panels are fine — usually a CT clamp or comms board). Production drops that don't match seasonal patterns (panel-level diagnostics via thermal imaging to spot dead cells or bypass-diode failures). Post-storm panel inspections (Long Island gets the occasional nor'easter or hurricane edge that loosens mounts).
Roof-leak callbacks years after install — we re-flash penetrations and fix any waterproofing failures. Critter intrusion (squirrels chewing wiring under panels) — we install critter guards to prevent recurrence.