I can only see three things happening
1 the developer abandoned the game
2 the developer died or something bad happened
3 the developer is working on a big update like heros harem guild or harem hotel or afterlife harem
lol or 4 dev is waiting on collecting a certain amount of money from supporters before releasing each new update. 5 dev has quit and just collecting $ from the 300+ supporters. And 6 the dev lost access/use of one of the games asset's from character’s or artist designs to music. Nowadays you need to have it in writing you can use assets in the adult game you are making even if it’s free content today it can change. Make sure the maker of the content knows what type of game you’re making. Or you will be like Eternum when they had to change their music midway through the game. Not all artist that give their gaming assets away will allow the assets they have made be used in adult games so get permission first. And screenshot the chat for your proof.