Poor after sales service

Bought a Sunsynk 8kw inverter 18 months ago. It has recently stopped working. Sunsynk informed me it would take two to three weeks to access the unit. I bought a 5kw Mecer inverter 6 years ago which is still working. It is unacceptable that the unit malfunctioned only after 18 months. Why does it take three weeks to access the unit? What about repairs? Well three weeks have passed. Not a word from Sunsynk. Extremely poor service.