Is the labour for Solar panels under warranty?

Hi I hope someone could give me some advice I had solar Panels fitted 4 years ago and for 6 months they have not been working. I was under the illusion that I was under guarantee but according to the company project solar limited I need to pay £300 for a call out appointment (labour charges). I feel a little duped and I was wondering if this the case or I need to pay for a call-out. Appreciate any advice as not had much luck with money recently. TIA