Unity Social Platform not working correctly?

I'm making a space shooter game for iOS and Android and whenever one of the enemies is destroyed, I report progress on an achievement. If I use Social.ReportProgress to report it, it does not work, there aren't any errors, but the progress is simply not reported. I managed to get around this problem by using a third party plugin, but I'd still like to know if I'm doing something wrong with my code? Also, is there a way to increment an achievement using SocialPlatform that works? I know that Google Play Game Services supports incrementing achievements, but I can't seem to find a way to do this using SocialPlatform. I realize that I could always buy Prime31's plugin, but I'd rather save the money if I can.

My current Social.ReportProgress code is as follows:

 Social.ReportProgress("achievement ID",10.0f,(bool success) => {
 });

I'm also confused on whether I should use the numeric achievement ID that is given to me in the achievements section of my apps home page on iTunes connect, or should I use the achievement ID that I set when I created the achievement? For example,

Should I use this,

Using Achivement ID given to me in iTunes Connect:

 Social.ReportProgress(123456789,10.0f,(bool success) => {
 });

or this,

Using the Achievement ID I created in iTunes Connect:

 Social.ReportProgress("achievement_ID",10.0f,(bool success) => {
 });

Thanks