The "more than one device/emulater" is more likely to appear after many attempts. It is an error that the program does not know which device to command because multiple devices are connected.
In nmap.sh, there is a workaround for this kind of situation, so it should be easy to succeed.
It is possible to work around it if you do everything manually, but it is tedious to type long commands, so rebooting as
@Endercraft said is quicker.
It may be difficult to automate the process since there are some puzzling phenomena such as adb tcpip 5555 becoming 555. We can only verify that it works in a typical home Wi-Fi environment, so it may be difficult to get it to work in your environment.
If possible, run adb tcpip 5555 with a USB connection to your PC and verify that it works with the plug-in. If this does not seem to work, we are out of luck.