It looks like https://sh.itjust.works/c/fossdroid@social.fossware.space isn't working because it's automatically making it to !FOSSdroid@social.fossware.space instead of !fossdroid@social.fossware.space
It works in other instances such as: https://feddit.nl/c/fossdroid@social.fossware.space
Home of the sh.itjust.works instance.