Sorry for the delayed response.
Could you let us know if you are seeing "not responding" message when trying to view a specific pdf or with all the pdfs?
Try rebooting the machine if you haven't already and check if that helps. If it doesn't, Run an Adobe program as administrator | Windows 7, Vista and check if you are still receiving this message.
Also, let us know dot version of Acrobat and the operating system installed on the machine? To check Acrobat version, you may refer to steps given in this link: Identify the product and its version for Acrobat and Reader DC