When saving command blocks as a structure, they won't run any commands inside them, when they get spawned into the world through custom dimensions.

When the command is say test, it won't run the command, nor does it return anything in the output box.

However, when the command is function example:test, it will return unknown function example:test, even though that function does exist and can be run manually.

A redstone source next to the command block (also inside the structure) won't help, nor does a repeating - always active command block work.

The only way to fix this is by switching the command block's state to needs redstone, and turning it back to always active.