It wasn't the first time. Server-side anti-X-Ray plugins had evolved. The old method of simple transparency no longer worked because the server would force a "default block overlay" on the client. Even if your texture pack said stone was invisible, the server sent a second layer of rendering data that kept it visible. Clever. Annoying.

The Ultimate Guide to Eaglercraft X-Ray Texture Packs: Fixed and Working Editions

Hover over the newly imported X-Ray pack in the left-hand column ("Available Resource Packs").

The Ultimate Guide to Eaglercraft X-Ray Texture Packs (Fixed & Working)

This guide will show you exactly how to and get a fully functional X-Ray pack for Eaglercraft.