Hi Sergio,
I have downloaded your current compiled demo, and it has the same issue, to recreate the problem please follow these instructions.
1) Download your Compiled demo's and extract 02.OAuth2_Authentucation from the 20.HTTP_Protocol folder.
2) Run the OAuth2_server.exe and change the port to 4500 (or any other port)
3) On this machines open up the port from step 2 in the firewall (We used 4500)
4) Start the server.
-- Local test --
1.a) run OAuth2_client.exe locally, change the configuration option to localtest, add the port :4500 (or the port you chose in step 2) for Auth and Token URL
2.a) Click new access token
3.a) The website will now load but you will need to accept the certificate, click allow, then enter the username: user and password: secret click sign in.
4.a) You will now have a success message in your local application with the expected results.
-- Network test --
1.b) run OAuth2_client.exe locally, change the configuration option to localtest, change the 127.0.0.1 to the ip of the machine running the server and add the port :4500 (or the port you chose in step 2) for Auth and Token URL
2.a) Click new access token
3.a) The website will now load but you will need to accept the certificate, click allow, then enter the username: user and password: secret click sign in
4.a) You will now have failed with the error Error Access Token: invalid_request
--- notes ---
Please ensure you can see the website, if you cannot then you will have a firewall issue which should be opened on the server as shown above.
I know its a bit overkill with detail here, but I wanted to make it easy for anyone else in the future to follow if needed :-)