Thank you for the prompt reply. I am glad that the cause of my problem was discovered though that for me means a new unforeseen expense.
How I could decide what to do, ask your cost estimates in $ for both cases.
I believe that the replacement modem economically cost effective compared to the cost of sending modem to upgrade, during which time there is no monitoring of the solar system. I believe that my solar system after replacing the modem behave exactly as required by the design. I hope that after replacing the modem would not be a problem with the remaining 2 older inverters (83CF and 83D4) that I bought in January of powerrme trade.
With inverters (83CF and 83D4) and the modem I was very pleased, although I noticed a minor problem. It is the following: When turned off power supply from a home network of more than about 2.5 to 3.5 minutes, the inverter does not start when I turn on the AC voltage. Energy production for the remainder of the day is lost. After sunset and sunrise again all is ok again. Both inverter behave equally. With the new inverter during the test have not noticed this problem.