i would much prefer being able to test it myself, but i would suggest you try these changes:
1) DELETE: j.Download(DireccionIpServidor & "/oauth/v1/tokens")
2) since you are sending the username and password as the body, you might try
to DELETE: j.Username="desarrolloquickin_Client"
j.Password="KD22E6p_rjObG-7NWzACpK"
3) DELETE: j.GetRequest.SetHeader("Content-Type","application/x-www-form-urlencoded")
REPLACE WITH j.GetRequest.SetContentType("application/x-www-form-urlencoded")
4) Your handmade urlencoding of the password is probably OK, but you should use a recognized urlencoder method to handle things like that.
final version would look like:
j.Initialize("", Me)
j.PostString(DireccionIpServidor & "/oauth/v1/tokens","username=OHIPSB_QUICKIN&password=Ly%7DbYD7%247l%2FU6%2Fe7V%23BFd&grant_type=password")
j.GetRequest.SetHeader("x-app-key","5171faa3-5308-49e9-aaaa-babbec18d478")
j.GetRequest.SetContentType("application/x-www-form-urlencoded")
j.GetRequest.SetHeader("Authorization","Basic ZGVzYXJyb2xsb3F1aWNraW5fQ2xpZW50OktEMjIyRkU2cF9yak9iRy03Tld6QUNw")