Help with vinyl planks on damaged subfloor
I have found that serious application of a CARBIDE "paint scraper" will remove some truly miserable adhesive residue in a purely mechanical fashion. Don't even bother with the steel blade types, they proved useless. 

Typically have a narrow tungsten carbide blade that is clamped, and has two sides so you can flip it once for a fresh edge before replacing or resharpening. Not even terribly expensive.