hola Natalia :)
me either, I dont have it so much clear, but I remember a post from admin, where he did mention about, so, if you have two times a 1-2 star rating, by the inmediate 10 last exchanges sent, I think you are not able to obtain addresses to send, so you have to negotiate with any of the two members rating you 1-2 star to upgrade to 3 star at least, or, wait that some of your exchanges in progress get to destination, always over 3 star, so you can move down the bad ones
at the end of the day, you need to have 10 exchanges with only 1 bad rating, this is what I understood