Error: "The operation cannot complete because of an unknown error [NOKY]" in Illustrator

Mine fixed when I changed it to RGB color mode. 

The problem is in the newest version, if you uninstall and go back to 27.3.1 and that will solve your Select all problem.

I found that only *some* objects / layers of illustrator art files were (no other word I can come up with other than "corrupted").  I ended up recreating thoses objects / layers from scratch and the entire art is now scalable with no issues.

FYI: I did not upgrade or downgrade software, just tested until I found the objects that would not scale dues to the noky error.

Also having this issue, scaling a logo with a legacy gaussian blur applied. Not sure why this is an "unknown error" as it has a very clear known cause.

i am having this same issue too, its not even a complicated document - literally only just started working on it its such a pain

I had the NOKY scaling issue today in Illustrator 26.1.

Luckily it was quite a simple object that I was working with.

I narrowed it down to examining the "Appearance" of one particular object in the "Appearance" window. There was an effect called "3D and Materials" that was listing although it wasn't visible (didn't have eye next to it). I clicked on this and then the bin icon (in this pane) and then all was good!

Continuing this conversation in hopes of a solution. It's March 2022 and we're on Illustrator 26.1. 

I'm adding myself to the list of users that is having this unknown error [NOKY] issue. The same as others here, it happens when trying to scale a object that has a legacy effect gaussian blur. 

The only work arounds to date are to:

• Revert back to a earlier version of Illustrator, be sure to save all of your projects back to the earlier version beforehand. 

• Expand the object, rendering the effect uneditable.

• Deleting the Legacy effect from the object and applying the current version of gaussian blur. Sadly, If you have a project which has legacy effects used extensively then your in for a long night updating them.

Until this issue is fixed could there be a script made that globally updates all objects in your project file using legacy effect gausian blur to the current gaussian blur effect?

SAME!!

If there's a workaround to this issue, sure would appreciate someone sharing it. 

I'm sure there are many more experiencing this that aren't commenting here and Illustrator help people are giving us the Comcast Customer Service cut and paste response. Is anyone over there at Adobe interested in fixing this??