lightmap usually baked to another wrong uv set but lightmap uv.

[suicaoya123]

i did`t do anything complex before ready to bake.because objects contain more than one uv set.

[LorenzWieseke]

Normally if you just bake a lightmap and check the unwrap checkmark a new uv will be created called "Lightmap". If you want to use your own uv map and not generate a new one, you need to rename it to "Lightmap"