deepslate tiles don't use the deepslate tile item to repair, instead, they use the deepslate brick item
this goes for all the tile variants

the normal nether bricks can't be repaired using the nether brick item
using the nether brick on the wall, slab and or stairs works fine tho

the normal stone brick block can't be repaired using the stone brick item
using the stone brick on the wall, slab and or stairs works fine tho

right click on a nether brick wall with a pickaxe gives the player normal bricks