The answer depends on why you can't get the signature. The law in every state requires that a person must sign a power of attorney authorizing another person to act
on his or her behalf.
In this case, the signing requirement helps ensure that your parent actually wants the power of attorney to be created. If he or she is physically unable to sign, however, your parent may direct another person to sign instead.
And depending on the state and the actual type of power of attorney you seek, the law may also require that the signature be witnessed, notarized -- or both. This helps to ensure another legal requirement is fulfilled: that your parent is of sound mind when the power of attorney is created.
So if you can't get the signature because your parent doesn't approve of the power of attorney, you will not legally be able to get the document. And if your parent can't sign because he or she lacks the mental ability to understand what is going on, that will bar you from getting the power of attorney, too. If you are in either of these situations, but feel that your parent needs to have another person to care for finances or medical care, your only option may be to go to court and get a conservator or guardian appointed to do the job.