PowerShell Resetting TPM
You can give some of the PowerShell TPM commands a shot by running them from an elevated (run as administrator) PowerShell command prompt to reset the TPM settings.
Clearing
See Clear-Tpm and Set-TpmOwnerAuth for further detail but below are a few to give a shot:
Clear-Tpm
Initialize-Tpm -AllowClear -AllowPhysicalPresence
Default Value
You may also want to consider looking over Initialize-Tpm and note that if you do not specify an owner authorization value, the cmdlet attempts to read the value from the registry so this may be reading and setting by default what you don't know from this value.
New Value
You may want to consider running ConvertTo-TpmOwnerAuth command to explicitly specify the new owner passphrase. So incorporate this into your process accordingly:
ConvertTo-TpmOwnerAuth -PassPhrase "<newpasswordstring>"
Configuring Local Group Policy Settings for BitLocker
As I said I'd do in a comment below a few days ago, below are the steps I take to setup TPM encryption on non-domain joined PCs in one of the environments I support.
NOTE: Please note that some of these options may have to
restart afterwards which I did not mention specifically but I don't
remember which ones exactly except for where I mentioned that. So if
it restarts or needs you to restart after setting an option, then that
is normal, I just didn't mention it.
During one of the restarts, the machine may detect a TPM
security change and prompt you to accept or reject the changes to
enable, activate, or take ownership of the TPM device. So you will
want to accept these changes if you get such a prompt after one of the
reboots per the changes to make mentioned below.
Go to Start > Run > type in gpedit.msc and press Enter
, and then navigate to #6 as in the below screen shot

You will want to set the settings from the above #6 location with the values from the two below screen shots next


Next go to Control Panel > Bitlocker Drive Encryption > select Turn on BitLocker and then press Next
in the window as in the below screen shot

On the Preparing your Drive for BitLocker window press Next
When the Drive preparation is complete windows pops up, click the Restart Now
option
After the restart, sign back onto the machine and when the BitLocker Drive Encryption setup window pops up, select the Next
option
When the Turn on the TPM security hardware windows pops up on your screen, select the Restart
option
After the restart, sign back onto the machine and when the BitLocker Drive Encryption setup window pops up, select the Next
option
You will then be prompted to Enter a PIN so type the PIN in both those fields as in the below screen shot and then press the Set PIN
option

When the How do you want to back up your recovery key window, you will want to press the Save to a file option and then press the Next
option. You will need to ensure you put this on a USB thumb drive and save this recovery key to it and then copy it somewhere else later such as a network drive, etc.

In the Choose how much of your drive to encrypt, in my case I've selected the Encrypt used disk space only since I do this for new PC setups, but you can select the most appropriate option here for your requirements and then press the Next
option

In the Choose which encryption mode to use window you will want to check the appropriate option for your environment but the one I select in this environment on my side is shown in the below screen shot

Also see How to Clear the TPM Chip of any previous Ownership Credentials and be sure to follow those instructions step-by-step if you've not already done so.
This article provides information on how to reset the TPM chip and clear all previous owner details.
You are unable to reset DDPA or DCP credentials on your system
You may encounter an issue whilst attempting to reset the DDP|A or
DCP credentials, where you are prompted for a Trusted Platform Module (TPM) ownership password.
If you have lost the TPM password, the TPM chip can be cleared using
Windows.
Notice: This will completely erase the TPM credential store, including hard drive encryption, fingerprints, smart cards, etc.
Please check which security devices you are using that may be
affected. Make sure you have a Windows password set up and set for
login.
How to reset and clear the TPM Chip
The first thing to do is to remove any pre-boot passwords in the
DDP|A console.
This will not affect the Windows password.
You must be able to validate just as in any credential scenario,
and you must be an administrator on this system in order to
perform this function.
Click Start. In the Search\Run box, type tpm.msc and press ENTER.
Under the Actions section on the right, click Clear TPM.
In the Clear the TPM Security Hardware box, check I don't have the TPM owner password and click OK.
You will be asked to Reboot. Just after the Dell POST screen, you will be prompted to press a key (usually F10) to clear TPM.
Press that key.
Once the system reboots, you will be prompted to restart and follow the instructions to enable TPM. Restart.
Just after the Dell POST screen, you will be prompted to press a key to enable TPM. Press that key (usually F10).
Note: If you do not use TPM, press the ESC key.
Once back at the desktop, either the TPM Setup Wizard appears for you to enter a TPM owner password or you can choose Change
Owner Password.
You can now clear DDP|A credentials through the DDP|A console.
For more information, please check out the article below :
source
OSManagedAuthLevel=2
means Delegated. You might try to set it to 4 (Full) and reboot, then clear again the TPM. Read the relevant parts of the article.