Some details: a check was done out to both my name as well as a automobile physique use we suspicion we would move a automobile to. The automobile was being financed. The automobile physique use can’t validate it over to my name.
Or should we ask Allstate to reissue a check (I do not own a automobile anymore) to my name alone?

You have to ask them to reissue to your name alone. Explain the circumstances and they probably will. After all, when you sell a car “as is” you get less for it, since the new owner will have to do the repairs. But don’t try cashing the two-party check without one of the endorsements. Your bank won’t take it.