serial receive block simulink

Hello,

I want to configurate the serial port used in simulink "serial receive" block. For some reason I can not select a port. This just appears "Please select a port..". When I click over "please select a port.." to select my port (COM3) no port appears, just "please select a port".

I have used "serial receive" block other times, and I remember I had the same problem but I can not remember how I solved this.

Maybe I am missing some kind of configuration. Any help will be welcome.

Thank you