How do I unstick a glass sliding curio cabinet door?

have you tried WD40? here are other ideas

https://www.hometalk.com/diy/repair/furniture/q-how-do-i-fix-an-old-sliding-cabinet-door-44396525

There is probably no hardware there for it to be able to move. If it is held in place by trim, tip the top of the door into the groove behind the top of the trim. Then push the bottom down into the groove behind the trim. That way you are relocating the door past the grooves.

Hi Heidi, there may have never been any hardware and the doors just bypassed each other, held in by grooves or small pieces of trim at the top and bottom. Try tilting the door up (into the groove or behind the trim). Push the bottom in and set it down into the bottom groove or behind the trim. Hope that makes sense.

Don't know if this will help but it is worth a try try pushing down on door that may compress the pin that should give you enough slack to slide the door.

A thin film of lubrication should be applied to the top and bottom of the door track. Tips: on vinyl door tracks, use a non-stick silicone lubricant. Instead of spray lubricant, use a hard wax like candle wax or beeswax if you have wood tracks

My response does not address the difficulty in getting the doors to slide; but I would just like to share that once you do get the doors sliding smoothly again, if you find that you do not care for the shallow indentations, the small Command crystal knobs work well for these kind of glass doors.

I have also found that the larger size are strong enough to operate sliding glass shower doors.

WD 40 or silicone lube

Try using WD-40 on slide or furniture polish sprayed in!

Check to make sure it is actually designed to move. My mother's cabinet is similar and there's one panel that doesn't open or move. If it is designed to move, spray with a white lithium grease on the hardware to loosen.

The doors lift up to remove them I have that cabinet they do move the wood is probably swelled

Is it possible to put some oil in the track? Hemp oil should work.

You might do some very close detective work first to make sure it’s not blocked in purposefully or not meant to move. I know it’s seem odd if it was meant to be fixed. If you get real in there, you might find the reason it’s not moving and hopefully it’s an easy remedy.

The top and bottom of the door track should be coated with a thin layer of lubricant. Use a non-stick silicone lubricant when lubricating vinyl door tracks. If you have wood tracks, use a hard wax, such as candle wax or beeswax, as opposed to spray lubricant. WD-40 on a slide or furniture polish sprayed in are other options!

It may be designed not to open. Although it’s a pain, I’ve seen many mcm pieces designed that way.