It is a derating message from the inverter.

What’s causing it, is something you will need to investigate further from the list in the link

You may need to check with Solis if you can’t identify the problem 

Thanks so much for your reply.

I have checked to make sure it's nothing I can fix and had an electrician check as well, he could not find the problem and advised to contact Solis. They unfortunately won't return any emails in regards to the problem I have sent them over the past few months 

If you look at one of the condition notes :

•If the internal temperature is between 40°C (104°F) and 60°C (140°F) the inverter will have derated to somewhere between 100% and 77% of maximum output power Above 60°C the inverter will stop producing power until the internal temperature lowers. 

you will see that at 84°C internally, the electronics are protecting themselves so unless you can improve the cooling around the inverter it will derate at that level. 

Hi

Thanks for your message 

Yes I have read that about the inverter. Mine hits over 60 degrees Celsius by about 9am in the morning, and for around six hours it's around 84 degrees Celsius. Most of the day it's over 60 degrees so is never really producing any power. I'm going to turn it off tomorrow as am worried it will set the house on fire. I'm tired of spending so much time trying to get answers as to why, so will just use grid power and put it down to a bad experience. I don't think I'll ever buy anything from china again, they must be sitting back laughing at us all. 

I do very much appreciate your time in trying to help out in this situation though 

I don’t know your location but in the UK (where this forum is based) we are around 12 °C currently and my system (not Solis) is sitting at 36°C. The internal temperature will depend on the weather and how hard the inverter is working. 
There will be specific models for different areas which is why it’s difficult to comment on tech from other regions but you might want to check that you have the correct model and fitment for your situation.