What do you call the inability to see alternative solutions to a problem?
This is called the Einstellung effect:


  ...Einstellung refers to a person's predisposition to solve a given problem in a specific manner even though "better" or more appropriate methods of solving the problem exist


It is related to the idea of functional fixedness:


  Functional fixedness is a cognitive bias that limits a person to using an object only in the way it is traditionally used. `