This is what was suggested to me on the SM forum and it worked: First, type out your serial number and save the text file so you can copy and paste in the following process, since you may have to do it more than once: (1) Go to your Programs folder on your C drive; (2) make invisible system folders visible (I don't know how to do this in W10); (3) Look for a folder named Program Data. Open it. (4) Look inside for a folder named "Poser". Delete it. (5) Re-launch Poser and you will be prompted for your name, s/n, and email. That worked for me.