A few steps are worth a try I think:
- try one of the other sources the dev provided (sometimes some vendors crave for payment and stop download on purpose at the very end to make you spend money)
- try switching the browser (Chrome/Firefox/Edge)
- try using a premium link downloader [with the permission of the domain owner of course XD]
- try downloading with VPN (use VPN Proton as it has a free mode and not being as slow as others), if it works it was a problem related to IP adress ban
- try finding downloads on other sources like archive.org
I bet, one of those methods will work for you! I can assure you, 'download other games now' is shit, because NO, REALLY NO VN HENTAI GAME IS BETTER THAN "ETERNUM"!