“The Group Policy settings for BitLocker startup options are in conflict and cannot be applied. Contact your system administrator for more information.”
Microsoft information in the GPO setting is incorrect. Try this:
under “Require additional authentication at startup”
– either you “allow” each option so you can choose which one when you set Bitlocker on,
– or you can “require” an option and disable all the others, so you will not be able to make a choice when you set bitlocker on.