What is this error/what does it mean?

##Problem

What the error means is you're trying to run the ProcessReceipt callback on the client, and not the server. ProcessReceipt will only work on the server.

##Solution

To fix this, all you have to do is move the code into a server script, and move that server script to ServerScriptService or Workspace.

##Tutorial

I tried making a dumbed down version of the wiki article as a response to a question a few days ago. If you want to check it out, here is the link.

https://scriptinghelpers.org/questions/27112/#30658

######Hopefully this answered your question. If so, do not forget to hit the accept answer button. If you have any questions, feel free to comment below.