I just had this issue. It's from having multiple strokes for the same path. So remove the extra one by clicking the ellipses on the appearance panel for the path and delete any extra strokes.

Could you make a reset button for those options. Like in AE effects (or even prefered presset even better!) . Thanks

I try to replicate and everything works fine for me.
Can you record a video?

Thank you Cassie, I just tried this and unfortunatly it didn't work. I tried it again and after the third attemp AI suddenly crashed...I'm frustrated. I've made this post over a year ago, by now, I have a new computer, newest CC version, always update everything, but this bug has been there the whole time. Just like the eyedropper bug (doesn't work on groups).

I don't get why Adobe isn't fixing this stuff. I know I'm not the only one with those problems, but instead of fixing this it's just new unessessary features with each update -.-

Okay so I've been having the exact same problem. I'd tried every thing possible and this is only thing that has worked for me:

So go to Window,
Select Appearance,
When the appearance box comes up, select the path you want to make dashed,
In the appearance box, select the stroke,
Delete the stroke by clicking the little bin (The stroke settings will be deleted but your shape or path will be fine and you can then basically reset it),
Now if you click on the stroke, you can apply your dash settings and stroke size and it'll suddenly work!

Hope this solves it for you x

Hi Anish,

I'm not the original poster but I'm finding what I believe is the same or related behavior. AI 24.2.3 on Catalina.

Here's what I do:

Start AI (fresh start is important)
New Document (RGB)
Pen tool, create a 2-point line
Stroke panel, click 'dashed'
Default is 12 pt in first dash field, with blank entries in remaining fields.
Click into first gap field. Use scroll wheel to change value. Set value to something else (20 pt for example).
Click on canvas to deselect line; gap value disappears and line pattern reverts as if I hadn't changed the gap value. (This is the bug) -- or --
Instead of clicking on canvas, I hit 'enter' (or 'return'; both tested); same result. -- or --
Instead of clicking, I tab to the next field (second dash field); same result.

How do I get around this?
Tab to the next field and change value; disappeared value in previous field reappears. -- or --
Toggle "dashed" setting off then back on; sometimes disappeared values reappear.

-p

I found a way around. Just enter second dash 0 and second gap 0 (2nd and 3rd field) and it will work. Evidently it's a big fat bug.

Having the same problem on win10, old documents prior update is working

Having exactly the same issue with V. 24.1.2 on Windows 10.

I have the same issue. Whether entering numeric values for the first gap or using the mouse wheel, the dashes show until I hit return or exit the value box, then the gap value disappears.

Hi Dana,

It would be really helpful if you can send a new and an old file with dashed lines in it. Please share the same on my id anish@adobe.com

Hi Anish,

1. I've tried different path types and even created new blank documents and recreated it, same problem.
2. Both, still same problem.
3. There's no one specific file where this occurs, it's happening with every new document I created since the last update.
I did notice however when I open older files (that I've created before the update and that feature dashed lines) it's working properly. I can even create new dashed lines normally, but only within documents that have been created with the older illustrator version. Would it help if I send you a new and an old file with dashed lines in it?

Using Illustrator CC 2020 V. 24.0.3 on MacOS Mojave 10.14

The dashed line effect cannot be applied. As soon as I make use of the gap field, I can see a preview but then when I click anywhere the effect just disappears. And when I try to create outlines it just turns into a normal non-dashed line.