According to cell theory, scientists do not classify a virus as living because it does not have?

Anything to do.

A virus is always dead, and it cant really do anything until it finds a host cell in your body, once they find a host cell they will multiply and then those viruses will have to find other host cells rendering them useless until they find a cell, therefore they are not living.

I don't know if thats the answer you wanted but thats the best I could do.