Hi @LarsR, yes I did refresh the catalogue and it worked. I was able to install Tailscale, piHole, and deluge. Nothing more. The log showed the ‘up’ action error. I will paste the log once I get back home in few hours.
Found a similar topic ( [solved] Unable to install Apps - network is unreachable - TrueNAS General - TrueNAS Community Forums) where it was advised to swithc off ipv6 etc. as I wrote in my initial post. But it did not work for me :/.