DP 8.1 uses a new licensing scheme. Normally, when you install DP 8.1, you have 60 days to get the new licenses, at no cost to you. Unfortuantely, when you imported the old licenses (I am somewhat hazy about how this was done), the 60-day grace period goes away
Please review the DP 8.10 Installationand Licensing Guide
Chapter 5
pp 242-261
The instructions on how to obtain the new licenses can be found on pg 254
You may also want to review teh Product Announcements Guide