Can't install any software from software center

Hello, I am using lubuntu 18.04 LTS. After installation all looked good and even I installed some softwares using deb pakage and software center and those softwares are still working. But after some days it seems impossible to install any software from software center. When I try to install any software it shows progress bar and after a few seconds it shows that software is installed. But when I click the lunch option the software doesn’t open and nothing happens. Moreover after restarting my pc I cannot find that software in the installed software list.
Can anybody please help me in this situation?

Thanks to all.

Which software are you trying to install that doesn’t work?

I can’t install any software from ‘softwares’(eg. nomacs, font manager and so on).

However there are some screenshot links of installing nomacs. that may explain my problem better.

I see no related bugs listed in gnome-software, which is what this application is. Additionally, I can install nomacs just fine with it. Once installed, I can launch it. If I search for it, it shows installed. It also shows up in the menu under the “Graphics” category. The only bug is that it doesn’t show in the list when you click the “Installed” button at the top.

I suspect you might have got yourself into some broken package state which is keeping you from installing software at all. You should try to use standard tools like synaptic or apt (on the command line) to see if there are any warnings or errors reported to give a clue as to what the problem is.

Also, I should add Lubuntu support for 18.04 is ending relatively soon. Since we have moved to an entirely different paradigm, there are very few common threads between the two. That said, I’d urge you to upgrade to 20.04.

Actually i am afraid to upgrade to 20.04 as it warned me in the release note.
However there is the output when i try to install ubuntu-restricted-extras using command line.

kumud@kumud-desktop:~$ sudo apt install ubuntu-restricted-extras
[sudo] password for kumud:
Reading package lists… Done
Building dependency tree
Reading state information… Done
The following additional packages will be installed:
The following NEW packages will be installed:
ubuntu-restricted-extras unrar
0 upgraded, 2 newly installed, 0 to remove and 22 not upgraded.
Need to get 0 B/132 kB of archives.
After this operation, 336 kB of additional disk space will be used.
Do you want to continue? [Y/n] Y
Selecting previously unselected package ubuntu-restricted-extras.
dpkg: unrecoverable fatal error, aborting:
files list file for package ‘m17n-db’ is missing final newline
E: Sub-process /usr/bin/dpkg returned an error code (2)

Once i tried to install this and then my pc hunged. Then i fourcefully turned off my pc. After that I encounter this problem.

There again, no bugs in in the m17n-db package. I’m not exactly sure how this is related to the ubuntu-restricted-extras package, as there don’t seem to be related dependencies. My guess is that this is a problem you had before trying to install ubuntu-restricted-extras. You might want to try sudo apt install --fix-broken.

Regarding the upgrade from 18.04 to 20.04, the issue is not that it’s going to break your system, nor is there some specific concern about 20.04’s stability (I’d argue it’s more stable than 18.04). What you’ll end up with is two complete desktop environments (LXDE from 18.04 and LXQt from 20.04) plus a whole suite of toolkit-specific applications (GTK from 18.04 and Qt from 20.04), meaning you’ll end up with a lot of redundancy which can lead to confusion. A fresh install solves any concerns… and would fix all your other problems.