Message states 'All Recent Media in this Category Liked'

This error code means that on the specific hashtag there are not enough recent photos in that hashtag for Robolike to like.  It might be best to take that tag off and replace it with a tag with more photos.

"But I see photos in that hashtags that are un-liked by me?" 

Yes, that could be for two reasons. One, Robolike has a built in content filter and it does not meet the systems requirements to like it. Or two, the photos are too old.  Robolike will only like more current photos.