127.0.0.1 is the loopback address. Ie it’s your computer trying to reach a service its hosting (prowlarr)/talk to itself. Sonarr/Radarr should be using this address as long as prowlarr+sonarr/radarr are on the same machine.
Prowlarr is either not running, or port 8080 is blocked by your firewall.
I tend to drop the link into yt1s.com
Sometimes just for audio, sometimes for the full vid.
I’m rarely grabbing more than one video at a time though.