Entity identification through type and name
Solution 1:
You're using the incorrect selector. Try:
tp @e[name="trainer"] ~ ~ ~
It looks for @e, all entities, and name="trainer", with the name trainer (case-insensitive).
You're using the incorrect selector. Try:
tp @e[name="trainer"] ~ ~ ~
It looks for @e, all entities, and name="trainer", with the name trainer (case-insensitive).