Go to Options > Resource Packs . You will see "Fullbright 1.12.2 (Updated)" in the left column. Hover over it and click the arrow to move it to the right column.
Open the Minecraft Launcher. Ensure your version is set to release 1.12.2 (or a Forge version based on 1.12.2). minecraft 1122 fullbright texture pack updated
Fix: You downloaded an X-Ray pack by mistake. Delete it. Genuine Fullbright keeps block textures; it only removes shadows. Go to Options > Resource Packs
No. A texture pack is client-side. It does not send packets to the server. It does not use X-Ray (which requires mods to delete block models). Fullbright simply tells your GPU to brighten the pixels. Go to Options >