Looks like little to no refrigerant is making it to the evaporator. This can be caused by 3 issues: a leak that has finally depleted enough that it isn't filling the evap at all, a restriction in the capillary tube that is only allowing a little of the refrigerant to pass, or a very weak compressor.

None of them are good news, but without a tap and pressure checks it is hard to tell which. On that one I'd guess it's a leak or restriction. There is a lot of steel tubing that runs through the cabinet and Frigidaire/Electrolux has had enough issues with leaks in that hot gas tube (yoder loop) that they've come up with an electric heater the repair person is supposed to suck through the whole loop and then bypass that part of the sealed system. Since it happened suddenly though a restriction might be more likely. I'd have to tap it at the compressor and see.

There are a few things you can check to help narrow it down.
1) Is there any oil on the evaporator? Leaks spit out oil too so a leak in the evap or at the joint between copper and aluminum will get oily.
2) Does the compressor sound normal, and is it running continuously?
3) If you have an ammeter check the amp draw of the compressor when it starts. Also is it very hot?

No matter what you are probably looking at sealed system work, which is usually $$$. Look at your owner's manual to see if it has a 10 yr sealed system warranty. That's probably the deciding factor. If you are paying parts and labor you will exceed $500 and maybe get over $700 depending on what is needed. The hot gas bypass kit technically makes nothing irreparable, and Frig/Elec will insist on it. However I've never heard of my one of my coworkers successfully install it. It's a nightmare solution that I hope to never try, as the hot gas loop runs around the edge of each door opening so is ~30ft long.

It might be worth the trip charge to have a tech diagnose, but expect bad news.