Try to open nhentai.net is browser after that open it in X Comic Downloader it may fix it, just maybe
I am really sorry for what happened, But I cannot fix it right now, I change house and I don't have access to WiFi. It take some time to change my old phone to new house for WiFi, without it I don't have good connection to test the App, with my phone internet I cannot even open the freaking site :(.
Please be patience, I will fix it when everything is OK. again sorry for the problem.