2015 Holden Trax

Hi all I have a 2015 Holden Trax, and we are unable to get the cover off the headlight to change a blown bulb. It's done up so tight my husband can't get it off. We've tried googling, CRC, silicone spray, and various tools. I have taken it to a mechanic who said to unscrew the engine cover and access it that way but that doesn't work either. Anyone have any advice? Thanks