I updated 2 days ago to Illustrator 26.0. I am doing basic pen tool drawing, no fx or anything fancy. After 10-15 minutes of working, it grays out and begins to say "(Not Responding)". I never had this problem with previous versions when doing simple line drawings. Is there some setting to prevent this from continuing. It's making it difficult to make any progress when it crashes in the middle of drawing.
The following is not a fix, just something to get you going again. The Adobe Creative Cloud App allows for multiple versions of Illustrator to be simultaneously installed. You could install and use a previous version while you sort out the issues with the current version.