Dear sir or madam:
The issue is that I am unable to login on my MacBook Pro. I am able to login on my other devices. My password, user name and email address are not in need of recovery. Please provide steps to troubleshoot this issue. 

I have just written wrote this to the Skype Customer Service

Hi. You haven't understood me. I know my password, my username and email. I don't need to recover y them it. I have access to the all three. The matter (situation / problem) is that the signing-in is not working with my MacBook Pro. My account works on all devices except the one I use, my MacBook. I think it has something to do with the incoming connection port, the proxy or something like that.

Present perfect tense: have/has + past participle

Note the difference between "I just wrote" and "I have just wriiten".

I just wrote a note. Yo sólo escribí una nota. 

I have just written a note. Yo acabo de escribir una nota. 

Although it's common for American native speakers to use the former when they mean the latter. 

I just wrote this to the Skype Customer Service

Hi. You haven't understood me. I know my password, my username and email. I don't need to recovery them. I have access to all three. The matter is that the signing-in is not working with my MacBook Pro. My account works on all devices except the one I use, my MacBook. I think it has something to do with the incoming connection port, the proxy or something like that.

Wow!  Excellent job, Carlos!  Just a few small corrections!  I am very impressed :)

Leigh