Best guess you have not setup nyaa correctly in Jackett. It is not sending over whatever is tagged as ‘input’ when trying to search. IIRC you need to have anime enabled etc. Don’t use so can’t provide specifics.
See here for troubleshooting https://wiki.servarr.com/sonarr/troubleshooting#searches-indexers-and-trackers
Perhaps think above moving to Prowlarr instead https://wiki.servarr.com/en/prowlarr