The outlines only show in the world when this pack sits above Faithful 64x, or above whatever base resource pack you use. If it sits below, the base pack's ore textures cover it and your ores look normal.
Setting the pack order
1. From the title screen or the pause menu, open Options and then Resource Packs.
2. In the Available column on the left, find Faithful 64x and the Faithful Ore Outlines pack.
3. Click the arrow on each one to move both into the Selected column on the right.
4. Look at the order in the Selected column. Packs higher in the list override packs below them.
5. Use the up and down arrows on each entry until Faithful Ore Outlines sits above Faithful 64x.
6.
Checking that it worked
- Load a world and find any exposed ore, such as coal or iron in a cave wall. It should have a bright colored outline around it.
- The surrounding stone, deepslate and other blocks should still look like plain Faithful 64x. This pack only changes ore textures.
- If the ores still have no outline, go back to the pack menu. Confirm that both packs are in the Selected column and that the outlines pack is the higher of the two.
With a different base pack, the rule stays the same. Keep the outlines pack on top so its ore textures win.