Makro (Brakpan) refuse to refund a Inverter that is not working how it should work.

We have bought a Gentech Hybrid Solar Inverter from Makro (Brakpan) in Nov 2022. We have charged the inverter for 48 hours as they instructed us to do. It was working fine for the first month then the inverter only last less than an hour. We have returned it back to Makro in Jan 2023 and they advised thay have to send it to the suppliers for inspection. They then advised me in Feb 2023 that we can come and collect the inverter. When I asked them what the issue was they advised me that they have replaced the batteries. We then charged the inverter for more than 48 hours before using the inverter. The inverter only lasted 2 months and again only now last an hour or less. We have taken the inverter back to Makro. Makro insist that it is the loadshedding that is the problem. We advised them that we have charged the inverter the full 48 hours and plus before using it again. Makro then advised that they get the technician to look at the inverter. Makro called us and advised us that the technician say that there is nothing wrong with the inverter. We advised Makro that we rather want our money back as the product is not working the way it should. Makro is refusing to refund us. We cannot accept the loadshedding as an excuse as we do not have allot of loadshedding in our area as they are *****ing allot of cables. We only had a TV and a apple box connected to this inverter so the load pulling from this inverter is not high.