Error - Operation in progress - MODBUS TCP/IP

[Fahd]

Enable persistent connection mode in the device settings. This error is caused by the Modbus device supporting only a small number of open TCP connections. You can also try rebooting the Modbus device if the error persists.

I still have the same error (I rebooted the LM5),  I get the same error even when I try to read data from an invalid IP.

The communication was okay until the Modbus device went offline for 1 month.