This is what I did, I took a Volt meter and measure the incoming voltage. If voltage is there, then you may have the wires reversed. The input + from the solar panel goes to the + cable to the AC200max. It is confusing with 4 input plugs. It is just a thought.
The way the male and female plugs are assembled there is only one way to complete the connection. So unless it is another factory error is is likely a firmware issue…which I cannot get instructions for updating.
Here is another trick that I found if you have a Volt meter. The other two plugs on the AC200max cable is parallel with the two plugs that you are using. So I connected my volt meter to the other two plugs and got 56 volts. Try it if you can.
Sorry, this trick only works on the EP500. But is could work if you have a “Y” cables to connect between the solar panel and the AC200Max.