Access-Control-Allow-Origin in server is set but still cant access

I started building with ionic and I want to fetch data from the server, the problem is with cross domain,
so as in all tutorials they say to add Access-Control-Allow-Origin

so I added, but still I get the same error on the ionic side, more details can be seen here:

@tzookb I use Allow-Control-Allow-Origin desktop browser plugin for chrome to test the api. This works when you are testing in the browser. I tried to run the app on my connected device and it did not had this cross domain problem.