GE WHOLE HOUSE WATER FILTRATION SYSTEM

I own the model GXWH20T and a few months ago the guy who installed it left the lever on “Bypass”. It is now stuck in that spot. I did turn off the house water supply, pressed the pressure release button, and still it won’t budge. I even opened the filter to see if that would make the lever unstuck and it won’t. How can I fix this? I just want to put the level to “Filter” 😢