Hi Everyone
just had batteries and Sunsynk inverter fitted. I was faced with the same connection issues as a lot of other folk on here seem to have and no matter what I, or the fitter did, the only way I could get WIFI was via my phone hot spot. I finally found a solution so am sharing as this may be useful to anyone else with connection problems.
I live in rural Wales and my home wifi is national broadband. This alone did not give a strong enough wifi throughout the house, so is boosted by a Deco unit with satellite Deco hubs throughout the house, my wifi strength is spot on so I knew this was not the issue.
SOLUTION, The Deco allows for an ISO to be set, this allows a devise to be wifi connected to that circuit alone and not included in the wifi circuit with all the other items connected in the house, which is typically everyone's phones TV's etc ect. This was an instant fix and the inverter is now happily connected to wifi.
I took a look at other routers / wifi boosters on line and most have this ISO function included so could hopefully, as with mine be the fix lots of folk seem to be looking for!
All the best everyone.