Hi there. My name is*****'m sorry that you're having this problem. I will be happy to help you with it. An online copy of the user manual for your Epson Workforce 3640 is available by clicking on the link below.
It is in pdf format and can be saved to your computer for future reference. It could also be printed but since it is over 300 pages, you may want to print only the relevant sections. The instructions for scanning begin on page 126.
Please review this document and give their instructions a try. Let me know how it works for you. If this solves the problem, would you mind taking a moment to rate my service? You can give your rating by selecting the stars located on the top right of the question page. I'd really appreciate it! Without a positive rating I am not credited for my answer. If this doesn't solve the problem be sure to let me know so we can continue troubleshooting.