Why doesn't Bitlocker encrypt the system drive?

Question

Windows

Good day! Windows 10 is licensed. In group policies "Require additional authentication at startup" in enabled mode, "Allow Bitlocker without TPM" is enabled. When trying to encrypt the system disk (physically disk 1, divided into 2 partitions), after rebooting, it gives an error: "Bitlocker could not be enabled
The Bitlocker encryption key cannot be obtained. Verify that the Trusted Platform Module (TPM) is enabled and ownership has been taken. If this computer does not have a TPM, verify that the USB drive is inserted and available.
C: was not encrypted."
The flash drive is inserted, it detects the flash drive when the system boots.