Have you tried uploading a picture?

This is pointless without telling us the model and posting a picture.

I would suggest plastic welding with a variable temp soldering iron and a 3D printing pen if the plastic is ABS. Then sanding the joints smooth. Acetone or glues are a waste of time because the thin binding surface cannot provide any strength.

Hot glue is for pasta arts and crafts and Teslas.

Epoxy/ fiberglass? It'd be very messy unless you know what you're doing though. My dad would also swear by araldyte or something similar. But I wouldn't recommend lifting your notebook by the corner after the fix.

I've never found a perfect solution for plastic, mostly because it depends on the type of plastic I think.

For the hard plastic of a notebook case, and a join that's probably gonna be under some stress, I'd try epoxy. Consider sanding it a bit so it grips the plastic better, and clamp it down to apply pressure as it cures.

I make zero guarantees about this approach, like I've said, never had a good time with plastic.

Yeah, that’s not very typical. I’d like to make that point.

Without some pictures I don't think I can give better advice than anybody else in here already provided. I repaired a busted hinge in an older HP Envy (huge laptop, high stress connection) with JB Weld. The hinge was metal with those heat-set nut inserts directly into thin ABS plastic so of course they ripped right out, straight from the factory. The repair has been holding for over a year now but the laptop sees very little use.

Goop adhesive.

Very strong, remains flexible to tolerate loads. Easy to apply.

Best thing about Goop - if you don't like how it works for a given problem, you can remove it! (It can be peeled off, though it's adheres very strongly.

I'd slather a bunch on the broken piece (enough so some will ooze inside the laptop and outside too), then push it in place and quickly rub off any that oozed out. Don't worry though, if you miss some on the outside, it can be rubbed off later after it cures - just don't pull on it as that will pull it out of the joint. Rub across the break - this will remove the excess without pulling it out.

That's where I'd start, and see how long the fix lasts. If it eventually did fail, then I'd use an epoxy like JB Weld/PC7. With JB Weld you want to have a solvent on hand to clean off any that oozes out onto the case (rubbing alcohol or Goo Gone, neither will dissolve the plastic).

I've sometimes used 2 adhesives like JB Weld and a couple spots of crazy glue. This would keep a piece in place with the crazy glue whole the JB Weld has time to cure.

I suspect you'd have success with one of these adhesives.