i havent been getting acheviments on my realm

Every time i would've have earned an achievement on my realm, i don't, i have fought the wither and should have gotten the haggler achievement, it started about a month ago when i realized that i wasn't getting my achievement, i thought if i just wait a few days maybe it will work, i forgot about it until now and i still haven't got the achievements, i have also tried downloading the realm to see if that would work, it didn't, please fix this me and my friends plan to fight the enderdragon soon and would like to get the achievement. my account is wispybassoon552