FT991A not working with CW Serial keyer

[DO8THW]

Hello radio friends, I have an ft991A and would like to use it with the CW keyer from LOG4OM, as I unfortunately don't yet know CW and would like to practice. I've already experimented with the COM port settings and also changed the settings for DTS and RTS in the program and on the radio, but in LOG4OM I either get the error message that the device connected to the system is not working properly, or if I select a different COM port, in this case Com4, I get the error message that access to this port was denied. Perhaps one of you can help me or tell me which settings I haven't selected or have selected incorrectly.
The Settings in my FT991A are:
31 CAT Rate = 38400bps
32 CAT TOT = 100 ms
60 PC Keying = RTS
62 DATA Mode = Others
71 DATA PTT select = DTR
72 DATA Port select = USB

[G4POP]

What interface cable are you using for com port keying?