Sequels to CYOAs are a pain to write due to the whole multiple endings thing. It’s generally the reason why I tend to avoid doing them, but you can still get around it a bit.
There’s basically 3 routes you can go (though you could even combine some of them)
1. Canon path
You just pick one path from the last story as canon and go from there. It’s an easy way of doing it since you’ve got a solid base to work with. If you’re using the same protagonist it’s almost necessary to do it this way.
Some people might get mad about how choices didn’t matter in the last story, but what the hell, it isn’t like they’re paying for this free entertainment and this isn't real life anyway, but an incredible simulation!
2. Time jump
You just jump ahead far enough that it doesn’t really matter what happened in the last story. You can still make vague references, and maybe imply some of the events happened or maybe they occurred differently (Just like a CYOA!) that nobody in the story even cares or has forgotten by that point.
It’s a little harder to write in some ways if you’re still trying to connect things, since you have to remember to do it very vaguely.
3. Same universe, far far away
With this, you can still do one of the above or neither, but you essentially put the sequel area so far away from the original area where the events occurred in the last story so they don’t matter at all. If there’s a time jump AND a different protagonist, it’s even easier.
