Unable to install "<PACKAGE>": snap "<PACKAGE>" has "install-snap" change in progress

Snap is probably still working on something in the background (or at least it thinks so). Open a terminal and run snap changes so see a list of ongoing changes.

$ snap changes
...
123  Doing   2018-04-28T10:40:11Z  -  Install "foo" snap
...

You can abort ongoing change(s):

sudo snap abort 123

Then you should be able to successfully install VLC through the software center, or through the command line using snap install vlc.

Open your terminal and follow these steps.

1. Abort the "vlc" snap process.

Inspect your snap "vlc" process by running command snap changes, this will show the status list of the snaps installations similar to this.

ID   Status  Spawn               Ready               Summary
3    Done    today at 22:29 WIB  today at 22:31 WIB  Auto-refresh 6 snaps
4    Done    today at 22:56 WIB  today at 22:58 WIB  Install "gitter-desktop" snap
5    Done    today at 22:59 WIB  today at 22:59 WIB  Disconnect gitter-desktop:home from :
6    Done    today at 22:59 WIB  today at 22:59 WIB  Disconnect gitter-desktop:pulseaudio from :
7    Doing   today at 23:21 WIB  -                   Install "spotify" snap
8    Doing   today at 23:24 WIB  -                   Install "vlc" snap

2. Pick the ID of your VLC snap process

Pick the ID of your "vlc" snap process, for the example 8

3. Abort the snap process by ID

Abort snap process by running command snap abort 8. This action will abort your vlc snap installation process.

4. Open your Software Center or running snap installation by a terminal

sudo snap install vlc

5. Wait for the installation until finished.

Open your terminal and type the below command in terminal.

snap changes

you will see the following results

    ID   Status  Spawn               Ready               Summary
3    Done    today at 17:04 IST  today at 17:10 IST  Auto-refresh snaps "core18", "gnome-3-34-1804", "snap-store"
4    Done    today at 19:59 IST  today at 20:01 IST  Install "stickynotes" snap from "latest/stable" channel

Note that id in this output . Here its 4(for sticky notes app). You need to abort that snap operation by running the below command.

sudo snap abort 4

After this try to install it again. If you still get that error restart your system and try again. And try to refresh your package also.

sudo snap refresh stickynotes

Thankyou , hope this helps!

In my case, you do not have to do anything, just wait until the application is getting installed. The installation process is not shown (I am not sure if it is some kind of a bug or feature) and it does the installation completely. Just sit tight and wait for it to get installed. It has happened and worked properly several times for me. Hope it works for others.

Same thing occured on my fresh 20.04 installation. Ubuntu asked to reboot while snap was installing two packages. Once the system has made its reboot, snap gui did not show any state of progress. With the snap changes cmd, you see that the state is "Doing" for the package that is installing. You can wait blindly 'till the end, or abort the activity with the id, and launch it again to see progress :

snap abort <activity ID>
snap install <package name>

Just like did Aditya Kresna Permana

I don't have any problem with the solutions above, but I have a suggestion according to my experiences.

If you use snap changes in the terminal, and you see that Status is Doing for vlc snap in your case, if you don't abort it, it'll probably install it.

$ snap changes

And after the installation is done, Ubuntu Software will probably give you a notification that:

VLC is now installed.

Application is ready to be used.