When it starts to thicken it's going off. You can try to thin it but it won't work well as a glue as the chemical action that cures the glue has been compromised. CA glue hardens using a chemical reaction rather than a drying action so it's not something that you can thin to restore like PVA or solvent based glues.

Just toss it. Or at least use it for VERY non critical areas but don't expect anything good from it.