Hello CPS,
For future reference, if re-installing, you don't need to actually "send off" the registration form. Simply use the information you received the first time you registered. The registration forms and licence info you receive subsequently must be filed away carefully in case re-installation is necessary.
Entering the system with an early date will trigger the 60 day limit thereby causing the temporary licence to expire "early".
If you have installed the latest version of Inventory Control (IC 8.1B) but still have an older version of the Lanpaks you will only have single user access in IC. As Steve indicated, you will need Lanpak 9.0B to provide multi-user access for IC 8.1B
If the above doesn't help, a quick call to your dealer, PwC Antigua, would set you on the right track.