I have a tiled pattern in Illustrator which appears in the Swatches. It's a simple pattern of wiggly line segments with black strokes and no fills. I want to edit this pattern so that the lines are green. I've followed Adobe's instructions on https://helpx.adobe.com/in/illustrator/using/create-edit-patterns.html but whenever I exit the Edit mode, the pattern becomes blank. This also happens when I do the "save a copy" command. Suggestions? Thanks
This may be somewhat of an X/Y problem. I think there may be something, which you are unaware of, that is causing your issues or there is an unfamiliarity with how pattern tiling works.
Note I'm not using the "bleeding edge" version of AI here, so it is feasible that there may be issues with that version. I wouldn't know. If any of the below fails then I may suspect a possible issue with the software itself.
Create the art and drag it to the Swatches Panel to create the pattern swatch. It's not going to line up perfectly.
Deselected all and then Double-Click the pattern swatch in the Swatches Panel to enter Pattern Editing Mode
From here you can reduce the tile size, then delete or reposition individual objects so they all align well, Pattern duplicates are dimmed for greater editing clarity.
Then merely click the Done link at the top of the Document Window and you should see the pattern applied with your edits...
If you see nothing in Pattern Editing mode, and the artwork is not white, there could possible be a software issue. But not necessarily...
Select > Select all to see if anything gets selected. Also, make certain you are zoomed out at least to see the entire artboard.
Entering Pattern Editing mode, centers the art on the artboard while you edit. If you are zoomed in, entering Pattern Editing mode won't zoom out, meaning the artwork may simply be out of view.