Have you purchased Premiere Elements 14 and are waiting for a purchased serial number from Adobe or whomever sold you Premiere Elements 14?
Or, are you just looking at the Premiere Elements 14 tryout for which you do not need a serial number, just click on Continue tryout until you decide to buy instead of try.
We are not Adobe here. Rather user to user. If you have purchased from Adobe, please contact Adobe Chat Orders to find out what happened to your purchased serial number. Check your computer email for an email to you with that information. Sometimes good emails get put in the Junk Mail. So, be sure to look there.
If necessary and it applies to you, please try the following link to Adobe Chat Orders.
Please give more details of your situation so that we can help you, user to user.