This article discusses the common problem when commissioning residential and commercial inverters (SUN2000L/L1 models, M0/M1/M2/M3 models).
Huawei inverters rely only on 2.4GHz frequency, which means they can connect only on the 2.4GHz routers.
Nowadays, more and more routers support both frequencies (2.4GHz / 5GHz). Also, they have a function called "Smart Connect" (as an example TP-Link, ASUS) which, if it's Enabled, will create a single, unified SSID (network name) that you can log into using a single password.
So instead of having 2 Wi-Fi networks (as an example: TPLink2.4 & TPLink5, you'll have only one SSID called: TPLink). Basically, this function means automatically giving each device access to every band and assigning it to the best one (when you connect a device to your router, Smart Connect will automatically identify the best available channel and assign the device to it).
This feature may be enabled by default on some routers. However, on the example of a TP-Link router, it had to be turned on and off manually.
If this function is enabled, the inverter will not be able to identify the network so as a conclusion, it will not be able to connect to it.
If this happens, please connect locally to the router's admin page (basically the locally connection page is 192.168.0.1 / 192.168.1.1 and use the Admin/password details which can be found normally on the router's back label) and disable this function, let your Wi-Fi router operates on both frequencies: 2.4GHz / 5GHz.
That would allow the inverter to identify the Wi-Fi router and to connect to it and to the management system.
In addition, try to not use it as an SSID name containing special characters (@#$%!*&, etc.), it may cause problems when the inverter will try to identify the Wi-Fi router.