It is helpful if you post the actual command you are running and all of the output instead of just some snippets.
This post has some suggestions which might be relevant: [HowTo] Work around gpg verification issue on left behind systems
It starts with a list of things to try, but if you scroll down you’ll see there is a handy script to run, like this:
export FILE=$(curl -s "https://forum.manjaro.org/raw/125822" | sed -n -r '/^###START###$/,/^###END###$/p')
bash <(<<<"$FILE") --help
You can try working through the various options starting with
export FILE=$(curl -s "https://forum.manjaro.org/raw/125822" | sed -n -r '/^###START###$/,/^###END###$/p')
bash <(<<<"$FILE") --basic