I am currently Emerald rank on the server and I was looking into upgrading my rank. I've been playing on the server for about 5 years now and purchased my Emerald rank when the website still used Enjin. I went into the store and went to purchase a rank upgrade and it said I did not have the required rank TO upgrade. The only reason I can think of is that it's because I bought it under Enjin and this is now XenForo. I do have photo proof of my rank but I do not have a receipt or anything.
What I’d recommend doing is sending in a donations email to [email protected]. In order to do so, you should check out this thread. Keep in mind that responses may take up to a week. Hope this helps and good luck getting this sorted.