Installing Fluka and Flair

Hello all,
Please I need your help.
I have been trying to install fluka and flair but still not successful. I read most of https://ryanstutorials.net/linuxtutorial/ .
Specifically, anytime I try to run sudo ./setup_wsl.sh (https://fluka.cern/documentation/installation/fluka-flair-windows10-wsl) the following is usually shown: Updating package list
W: GPG error: https://flair.web.cern.ch/flair/download/ubuntu/18.04 InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 5840F43443ADF6C1
E: The repository ‘https://cern.ch/flair/download/ubuntu/18.04 InRelease’ is not signed.
W: GPG error: https://flair.web.cern.ch/flair/download/ubuntu/20.04 InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 5840F43443ADF6C1
E: The repository ‘https://cern.ch/flair/download/ubuntu/20.04 InRelease’ is not signed.
[ERROR] Couldn’t update pacakge list. Try again later.

Dear Saheed,

try resetting the WSL Ubuntu app. See section 5 of https://fluka.cern/documentation/installation/fluka-flair-windows10-wsl

Then run again the setup_wsl.sh script.

Cheers,
David

Thanks so much for the guidance