Wifi Not working after sometime in Ubuntu 21.04

Recently I have installed Ubuntu 21.04. Soon after the installment I found out that the Wifi is not working after sometime. The available network list is continously loading and there are no networks on display. Even if I toggle the wifi from the settings to on and off it is not working. Only after a restart it starts working.

Initially I tried to run the following commands:

sudo service network-manager restart

and got the following output:

Failed to restart network-manager.service: Unit network-manager.service not found.

However, on running these commands I did not receive any errors but the Wifi was still not working.

sudo service NetworkManager stop
sudo service NetworkManager start

I also ran the following command:

systemctl list-unit-files | grep -i network

and here is the output

networkd-dispatcher.service enabled enabled
NetworkManager-dispatcher.service enabled enabled
NetworkManager-wait-online.service enabled enabled
NetworkManager.service enabled enabled
systemd-network-generator.service disabled disabled
systemd-networkd-wait-online.service disabled disabled
systemd-networkd.service disabled enabled
systemd-networkd.socket disabled enabled
network-online.target static -
network-pre.target static -
network.target static -

I ran lspci and found that my Network Controller is:

Network controller: Intel Corporation Centrino Wireless-N 2230 (rev c4)

I am beginner to Ubuntu. My most of the tasks are maily for personal work like study, wastch movies and surf the internet.

Any help is much appriciated here.

Many thanks.

Your wireless may be dropping because of power management; that is, the feature where the card partially powers down to save battery power during periods of inactivity and then, ideally, powers back up seamlessly when activity resumes. Let's disable power saving to see if it helps. From the terminal:

sudo sed -i 's/3/2/' /etc/NetworkManager/conf.d/*

Is there any improvement?

EDIT: Your wireless may be dropping because the channel to which it was connected has suddenly changed.

Please check the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, you may have better connectivity with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz, although it is likely to affect N speeds. I recommend a fixed channel, either 1, 6 or 11, rather than automatic channel selection. Also, be certain the router is not set to use N speeds only; auto B, G and N is preferred.

Your wireless may be dropping because there are two wireless access points with the same name and password. This is typical when you have a 2.4 gHz segment and a 5 gHz segment of the same router. Your wireless may be roaming, looking for a better connection. If this is the case, I suggest that you rename the access points; something like myrouter2.4 and myrouter5.

After making these changes, reboot the router.

Next, I recommend that your regulatory domain be set explicitly. Check yours:

sudo iw reg get

If you get 00, that is a one-size-maybe-fits-all setting. Find yours here: http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2 Then set it temporarily:

sudo iw reg set IS

Of course, substitute your country code if not Iceland. Set it permanently:

sudo nano /etc/default/crda

Change the last line to read:

REGDOMAIN=IS

Proofread carefully, save and close the text editor.

Any improvement?