Can you confirm that you have the warp upgrade? You can see all items you have in the pause screen (escape key should open that)
What I'm fishing for is whether you still have the item or not, and didn't quit the game without saving since you got it. Because I can't really think of anything else that would cause this item to not work.
If you've checked and are 100% certain that you have the item, could you email me a copy of your save file? You can find my email on my itch page.