Access to com port denied

Does anyone know what this means?
I’ve checked and double checked the settings, but the printer setting window is different to the manual.

UNBELIEVABLE!!! It looks like Repetier doesn’t recognise low com port numbers (something to do with the old serial connectors?) I changed the com port from 3 to 20 and no problems.

[quote=“Binny”]It looks like Repetier doesn’t recognise low com port numbers (something to do with the old serial connectors?) I changed the com port from 3 to 20 and no problems.[/quote]The real reason is probably that other software on your computer is automatically locking these lower end ports. Examples are bluetooth communication software.

I have the same issue but I have changed com port to 24 and then 30.However after a day or so it says access to the com port is denied?