When using the converter (terminal server) M031 with other than no parity (ie with even or odd), 8 bits of data are transmitted plus one of these parities - a total of 9. Therefore, it is necessary to set switch 4 to the ON position, ie 9 bits. Otherwise it will not work.
We have encountered this, for example, with EMU meters during M-Bus transmission (even parity) via Ethernet using WZC-P60 via RS485 interface, ie M-Bus assembly - WZC-P60 - (RS485) - M031 - (Ethernet) - PC.
The same applies to other converters with parameter setting using pianos (eg M011).