Channelling does not work in survival mode.

When a mob is struck by a trident enchanted with channelling, no lightning bolt is summoned. This can be replicated by:

1) Setting your game mode to survival; then

2) Obtaining a trident with the channelling enchantment; then

3) Summoning or finding any mob; then

4) Using commands to set the weather to 'thunder'; then

5) Throwing the trident at the mob.