WIN7 Bitlocker

Currently have Sales staff traveling the country. Quite frequently their Tablet computer suffers from Bitlocker issues, users are constantly getting requested to enter Windows Bitlocker Recovery Key. This is happening at the time of starting the system. I have checked all the systems TPM Security within the BIOS and they are all set to ACTIVE.

Machines are HP and Dell brand using Solid State Drives.

Can any one point me in the right direction to properly correct this?

Thanks in advance.
Grant