Hi there,
I encountered this issue (I'm a noob) and I'd like to document how I solved this for anyone that stumbles upon this in the future. Here's what I did:
First
I stopped the services I thought were relevant. I used the instructions from here: https://www.wikihow.com/Restart-Services-in-Linux
What I did was open the CLI (either through SSH or on device) and typed:
ls /etc/init.d
Then I looked for services that seemed relevant, In this case I was looking for anything with NUT(network UPS Tools) or UPSD.
I found two services called nut-server and nut-client.
I then typed:
sudo systemctl stop nut-client
sudo systemctl stop nut-server
I then could enter the web interface and enter my information and click apply without an error message. After that, I restarted the PC and everything worked.
MY understanding is it is necessary for you to have driver, port, and description fields filled in, everything else isn't necessary.
What I tried that didn't work/My questions:
I tried following this guide here:https://www.systutorials.com/docs/linux/man/8-upsd/
and trying upsd -c stop but the system kept telling me upsd.pid(I think) was not found.
I interpreted that to mean that the system is attempting to shutdown via using the configuration file but that file didn't exist. Can someone help me understand?
Thanks
Best of luck to everyone and hoped that helped