My husband is in a nursing home with frontal lobe dementia. I have a refund check from Allstate insurance. Bank will not cooperate. Advice?

This is the time for you now to get a POA assigned. Do you have family willing and able to assume financial POA for you? This is unlikely to be the first problem. Your husband is already unable to sign to designate a POA. There are financial fiduciaries willing to do this work for a fee. I would contact the administrator at your nursing home to ask if they can help you find a way to deliver this check with your signature and a deposit check. In these days banks often don't even require an endorsement for deposits to your own personal account. Speak to the administrator and see what ideas he or she can give you.