No internet after modifying /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf

I suffer from a slow internet on Ubuntu 20.04 hosted on a VM. I followed the solution in Ubuntu 20.04 Network Performance Extremely Slow

namely in /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf I modified the wifi.powersave value from 3 to 2, saved changes and rebooted.

After this change I have no internet. Also after modifying the wifi.powersave value back to 3 and rebooting I have no internet.

ip route show

gives an empty output.

nmcli connection

gives

Error: NetworkManager is not running

sudo systemctl restart network-manager.service

gives

Job for NetworkManager.service failed because the control process exited with error code. See "systemctl status NetworkManager.service" and "journalctl -xe" for details.

systemctl status NetworkManager.service

gives

● NetworkManager.service - Network Manager
     Loaded: loaded (/lib/systemd/system/NetworkManager.service; enabled; vendor preset: enabled)
     Active: activating (auto-restart) (Result: exit-code) since Tue 2022-11-08 16:47:36 EET; 20ms ago
       Docs: man:NetworkManager(8)
    Process: 6001 ExecStart=/usr/sbin/NetworkManager --no-daemon (code=exited, status=1/FAILURE)
   Main PID: 6001 (code=exited, status=1/FAILURE)

Nov 08 16:47:36 v systemd[1]: NetworkManager.service: Main process exited, code=exited, status=1/FAILURE
Nov 08 16:47:36 v systemd[1]: NetworkManager.service: Failed with result 'exit-code'.
Nov 08 16:47:36 v systemd[1]: Failed to start Network Manager.

journalctl -xe

shows a problem:

-- A start job for unit NetworkManager.service has begun execution.
-- 
-- The job identifier is 2760.
Nov 08 16:32:50 v NetworkManager[3819]: Failed to read configuration: file /etc/NetworkManager/conf.d/.#default-wifi-powersave-on.conf not found
Nov 08 16:32:50 v systemd[1]: NetworkManager.service: Main process exited, code=exited, status=1/FAILURE
-- Subject: Unit process exited
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support

What could I check and fix?

--

I was able to fix the problem by

sudo ln -sf /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf /etc/NetworkManager/conf.d/.#default-wifi-powersave-on.conf