I had a similar problem and use all sort of solvents till I realized that wasn’t glue but a flaw of the vinyl.
I looked like it was working when still wet but as soon as it dried it come up again.
You can tell because of the texture, if it is glue you must feel the texture when touching it with your finger, if it feels exactly the same than the rest of the floor … don’t bother is just a flaw.
Vinyl comes with loads of flaws, I found at least one in every pack when I did my room, you have to pay attention while installing it, later it’s too late.
Are you sure is glue?
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