You can't prevent someone from sending funds to a crypto address.
An address of an insolvent company may not be able to legally return funds; i.e. once they receive funds they may have a fiduciary duty to distribute them in a certain way, for example by order of a bankruptcy court.
tl;dr: They may only be able to ask people not to deposit, but not prevent them from depositing. And if users do deposit, they might not be allowed to give it back.
An address of an insolvent company may not be able to legally return funds; i.e. once they receive funds they may have a fiduciary duty to distribute them in a certain way, for example by order of a bankruptcy court.
tl;dr: They may only be able to ask people not to deposit, but not prevent them from depositing. And if users do deposit, they might not be allowed to give it back.