In Windows 11/10 and TPM 2.0 now, the BitLocker PIN length was increased to 6 characters. Also, the TPM 2.0 lockout period is greater than the default when a PIN is changed.

Input the BitLocker recovery key. Wait until the unlock period expires, and then enter the correct PIN. Reinstall the operating system, and then reset the TPM chip.

MBAM 1.0 included a Recovery Portal that the help desk could use for PIN resets, and BitLocker recovery issues, but it still required that the user call the help desk for assistance.