My mums and my father in laws roof pv systems produce next to nothing compared to their system sizes. One is 12 panel, one is 15 panel. In fact, My mums place was already installed (circa 2010) when she bought it and it looks like they haven't been producing for a while.
Likely the inverter but isn't worth fixing when doing the math, be breaking even over a full 10yr period.
They're not worth the cost tbf. It's BS.

Liz truss will sort it....... We'll all be in debt for years to come via government loans somehow. That's how Britains economy works, it relies on debt. The more debt there is, the more it earns. It's all wrong man!.