Uploading images/videos not working?

Whenever I try to make a post and attach an image or video to it, I see this in an error popup:

    
{"data":{"error":"unknown","message":"Request error: error sending request for url (http://pictrs:8080/image): error trying to connect: tcp connect error: Connection refused (os error 111)"},"state":"success"}

According to the instance rules there's a 20MB size limit on uploads but mine are definitely below that.