UPDATE:We found the fix for this problem. We set the SATA operation in the BIOS to AHCI instead of RAID, and now it properly shows the Bitlocker recovery when locked out.
Hi,We have Dell Latitude 5420 laptops that don't boot into the Bitlocker recovery environment when a user is locked out, forcing us to do a reinstall. When trying to unlock the drive using the recovery command prompt, the disk doesn't show up. However, when I boot into a Windows installer and use the command prompt from there, the drive does show up. When trying to unlock the drive using the command prompt, it gives a success message, but when restarted, it ends up at the same recovery screen as before, no bitlocker key prompt.The strange thing is now, Dell is currently replacing both the motherboard and storage drive, while this is not needed, if we reinstall the laptop, all hardware is working correctly.Looks like Dell is following a process but does not want to hear there is an issue in the BIOS or in the partition manager on the 5420 laptop.We can reproduce this issue on multiple 5420 laptops, but on other models we have, this issue does not occur. In my opinion, this is not a hardware issue, but more a software or BIOS issue.
Dell Latitude 5420: When locked with Bitlocker, laptop doesn't boot to 
Bitlocker recovery