Activation of Network Connection failed on Ubuntu 20.04

[Wrichik Basu]

I am facing this issue since some months on my laptop running Ubuntu 20.04. The WiFi disconnects suddenly and cannot reconnect, and an error message is shown in the Notification saying "Activation of Network Connection failed." This is not a problem with the router because just a few days back, I changed our WiFi provider, and they installed a new router, but I faced the problem today once again. Moreover, when this occurs, I can still connect and access the internet on the same WiFi network on my phone.

Note that when the WiFi disconnects, I can still see all the available WiFi networks, but the system can't connect.

The issue occurs arbitrarily now and then, over both 2.4 GHz and 5 GHz network. I have tried to restart the network-manager using sudo service network-manager restart, but it doesn't help. The only way to solve the problem is to restart the laptop. That is very irritating for me because I am often working with a number of applications open simultaneously like Android Studio, MATLAB, Texmaker and so on (and Chrome), and restarting the system means I will have to re-open them all over again. (Generally, I do not shut down my laptop; I suspend it overnight and wake it up in the morning.)

Upon searching, I found a number of websites like this one, but none of the solutions really worked (other than restarting). To be honest, I am not sure where exactly the problem is occurring. Are there any log files that I can check to find out why the problem is occurring?