@Eimantas, thanks for the comments, this is exactly the case.
@Colin, if you want the objects inside of a group to change the color, you have to modify the options for the tool.
Pick Eyedropper tool, press Enter to open the Eyedropper Options dialog, and uncheck both Appearance options above. This would prevent assigning the appearance of the green rectangle to the whole group (because that’s what applying appearance means).
However you are right, this is not normal. The sampled fill (as I see it) should have been applied on top of the contents, and not below — I assume this is what you are seeing in the Appearance panel when you select the group.

@Eimantas That worked! Thank you. I do find this functionality strange, though. I would like the actual objects within a group to change color when using the eye dropper tool.

@Colin. In your example, the group of black squares got a green fill when you copied it from the green rectangle. The green fill is not visible because it is behind the contents of the group. You need to bring the green fill above the 'contents' in the Appearance panel. I just wish Adobe maintains this functionality in Appearance attribute stacking and does not make Illustrator more simple because a lot of requests in this thread.

@Eimantas This does not appear to be my issue. The appearance panel is not showing multiple fills so I don't think the fill is being hidden by a stack of fills. I've been using Illustrator for years and this appears to be new behavior to me. Perhaps a setting somehow got changed but I have not been able to locate a setting to restore previous functionality.

Some people here have no idea how Appearance and Groups work in Ai and get frustrated. Object can have a separate set of Appearance attributes to a group. So, the fill of the object can be a different colour than the group that it is enclosed in. Also, fills can be hidden by other fills stacked above them. That is why you do not always see the effect when you copy a fill to a group. To understand and see how the attributes interact and are stacked together, one needs to use Appearance Panel.

Sure can, @Egor. Thanks!

@Colin, please share the test file and the recording of the attempt to make it work (and the but with the collapsing dropdown as well).
I want to see what’s happening and how I can help.

I am just now experiencing this bug and I'm disappointed to see it has been happening to people for 5+ years. This is extremely frustrating. I hate to have to switch to a new tool but it's looking like I'm going to have to. What's the next core feature that will break and not have a fix for 5+ years?

I have tried toggling the various eye dropper settings and nothing worked. I also found the checkbox menu for editing settings buggy itself (if I hover over a setting it collapses the dropdown).

toggled my eyedropper settings. still need to ungroup to change color of a grouped object. The swatch color in the toolbar on left appears correct, but color of objects doesnt change.

Heh, Ai has a lot of rivals today :)
Panos, do you have both Appearance options checked in the Eyedropper tool’s options?
Sampling groups and other objects differs a lot with these. Try to toggle them and see if it starts to behave as you expect.

January 2024 and the eyedropper tool is STILL NOT WORKING!

that's monopoly for you...if there is no competition you don't rush to fix anything.

adobe do better (oct 18, 2023)

Same issue, eyedropper tool doesn't work on groups.

The workaround I found (prepare for a ridiculous one, but what you gonna do):
- select the group you want to change color of,
-Cut,
(- get outside any group it may reside in if the case)
-Paste in Place,
-Ungroup,
- change color, with Picker on otherwise,
- Group back,
- Cut,
(- get inside the larger group it was in)
- Paste in Place.

This bug now no longer has the work around of holding the shift key while using the eyedropper tool. There has to be a fix for this.

Egor, you are a hero, thank you!
This problem popped up out of nowhere for me and i didn't realize why but after reading your solution I remember checking the appearance box in the eyedropper options and turning it off has fixed it.

As many others have come here to say, the eyedropper tool does not work with grouped objects. This bug has been documented for FIVE YEARS and no resolution has been proposed. It is CRIMINAL that Adobe is sitting on their hands on this one. Five whole years and not a peep from them! How dare they charge as much as they do if they refuse to address issues like this? Absolutely unacceptable. I am here to DEMAND that this bug be resolved. FIVE YEARS?!? Not ok.

The bug I am experiencing affects grouped object. When I try to change their appearance with the eyedropper tool, the color changes in the properties panel, but it does not change the actual color of the object.

MacBook Air (M1, 2020)
MacOS Monterey 12.4
Illustrator 26.5

Found thhis video that explained to hold SHIFT KEY , and PROBLEM SOLVED

Same problem here. Doesn't have any sense.