I have about had it with this thing. It came with the house and is supposed to open onto the deck. We are injuring ourselves trying to push it open on the track, and it’s not just because of the snow and cold, it requires a real effort all year round. WD40 doesn’t help much, I think it’s off balance and needs adjusting. What should I do?
I was having a similar problem with the screen doors on my door walls. The bottom wheels were rusted/corroded. Spraying them with WD40 let them spin a little, but switching them with the top uncorroded ones was what helped. In your case, I don’t know if there are top wheels you could switch with. You could probably find replacement wheels at Home Depot/Lowes, but you’d still need some time to replace them. More of a summer project.
You could could try looking at the bottom of your door to see if there is anything that looks adjustable. On my screen door, there was an adjustment for how high/low the wheel was, adjustable using a screwdriver. That also might be the problem.
You’d need to pick a day that’s not too cold, and have some way of covering the opening while you examine the door bottom.
Yes, there should be some sort of adjustment screw for those wheels. It may be well hidden though.
It adjust the wheel height up/down. Screw it too far one way and the door can get so loose it comes off its track. To far the other way and the door is basically always jammed.
check the adjustment. also check to see if its on its track right now. They can also be off track enough to function but still not properly.
And in addition to all of the above, The wheels have ball bearings which could be worn out. In my last home, I replaced the wheels on my sliding glass door about every 2 years for the 10 years I lived there. The house before that, I never replaced them in 13 years time. This house has no sliding glass doors 
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Keep in mind WD40 is not really meant to be a lubricant - it is more of a solvent designed to unstick things. Also, if the door is exposed to freezing temperatures, you want a lubricant that will not freeze or thicken in the cold. I recommend Triflow - it is sold as a lubricant for bicycles operating in winter conditions, but works well for a range of applications.
Here’s a video on how to clean and adjust your sliding glass door.
My hunch is that your door is out of square. The video shows you how to adjust the alignment plus how to properly clean and lubricate.
Thank’s y’all for the information. We’ll have to wait a few months until the world unfreezes.