Thank you for the additional information. You should be able to achieve successful communications with this setup. Are you receiving an error when doing this? If so, what error? If not, what makes you believe communications is not successful? Please detail what you mean by, "There was no success."
I don't understand what you're trying to do by placing a jumper wire across the ends of R7. This shorts A and B together. Luckily, according to the datasheet, the MAX485 driver's are short-circuit current limited and it has thermal shutdown circuitry, otherwise you would have damaged the MAX485. There is no possible way this could have resulted in successful communication. Your indication of "connected" or "not connected" must not be reliable and is not providing you with the actual status of the RS-485 communication.
In order to identify where the problem lies, please follow my previous recommendation:
Please verify that the inverter is still successfully working using your computer, Modbus Poll, and USB/RS-485 adapter. Please also verify that the Arduino/MAX485 board are still successfully working using your computer, Modbus Simulator, and USB/RS-485 adapter.
Regarding connecting a MAX485 transceiver directly to your Arduino using a breadboard, you could certainly give this a try, but I doubt you will see any difference versus the MAX485 board that you've removed R7 from (assuming that board has not been damaged). If you do try this, you will need to have a pull-up resistor on the RO signal, since that output from the MAX485 is high impedance when RE is high. You may be able to simply enable an internal pull-up on the Arduino's RX pin in code:
Thank you for responding!
After removing R7, I still get error E2 (timeout error).
Sorry, I also don't really understand what happened when connecting the resistor terminals, but what appeared in the serial was what I expected to get (figure 1).
To use only the MAX485 CI I need to put only one pull up resistor (10kohm), ok?