Win 10 RTM IoTEnterpriseS OEM:NONSLP

Actually as I think there is no MAK-key for Win 10 IoT Enterprise LTSC since that's "embedded" OS.

ananya.choudhary20@*.com  
See also my comments here

I didn"t see any MAK-key for Win 10 IoT Enterprise LTSC 2021 so far. 
If you"re interested you can enter key - KBN8V-HFGQ4-MGXVD-347P6-PDQGT (generic KMS-key for Win 10 IoT Enterprise LTSC 2021) - via Command Prompt and try to get KMS activation. 
Run CMD as Admin and enter something like this:

cscript.exe "%windir%\system32\slmgr.vbs" /ipk KBN8V-HFGQ4-MGXVD-347P6-PDQGT  [Press Enter]

cscript.exe "%windir%\system32\slmgr.vbs" /skms kms.digiboy.ir   [Press Enter]

cscript.exe "%windir%\system32\slmgr.vbs" /ato    [Press Enter]

Your OS should be activated for 180 days with KMS. 
Then if you want to turn back to Win 10 IoT Enterprise LTCS with a digital license you just need to enter any of OEM Keys in Parameters 
KDM9K-7NQCR-Y384P-G2YWJ-TQ9V7
R7NG3-7R8W8-KMKJR-TR6H3-BHCMV
FTRNB-J478C-7C6HH-48RH2-27MRH 
QPM6N-7J2WJ-P88HH-P3YRH-YY74H
and hit Activate.

Actually, where did this key come from:
https://windows64.net/453-windows-10-iot-ltsc-hwid.html

ananya.choudhary20@*.com 
You are right in your reasoning

With the help of these keys we can only upgrade ltsc 2021 to  iot ltsc  2021 but can’t activate the system because these keys are very very old and now blocked by Microsoft.
Every key I tried online it’s giving me 0xC004C003 
this error 

Yes, sure, if it"s blocked, only you can do with them is use for upgrading. 

I tried activate the normal ltsc 2021 version with mak keys they are working fine and Microsoft is giving confirmation ids 
but in case of iot ltsc 2021 there is no such option 

If you already have a digital license on your Windows 10 IoT Enterprise LTSC 2021 and will try to reactivate it with any of this keys you don"t need any CID. Just enter any of them in Parameters and hit Activate. But that"s completely useless action.

With the help of these keys we can only upgrade ltsc 2021 to  iot ltsc  2021 but can’t activate the system because these keys are very very old and now blocked by Microsoft.
Every key I tried online it’s giving me 0xC004C003 
this error 

eenigma702@*.com  
I can"t get what you"re trying to show.
Any of these OEM Keys are capable for upgrading from Windows 10 Enterprise LTSC 2021 (Desktop edition) to Windows 10 IoT Enterprise LTSC 2021.

KDM9K-7NQCR-Y384P-G2YWJ-TQ9V7
R7NG3-7R8W8-KMKJR-TR6H3-BHCMV
FTRNB-J478C-7C6HH-48RH2-27MRH 
QPM6N-7J2WJ-P88HH-P3YRH-YY74H (generic) 

ananya.choudhary20@*.com  
Correct. This key - QPM6N-7J2WJ-P88HH-P3YRH-VY74H - is default OEM Key for Win 10 IoT Enterprise LTSC 2021.
Any HWID activator installs default OEM Keys for specific Windows edition during activation process. 
See here and here 
If you have digital license on some OS, it will show you default OEM Key for this edition regardless what key you entered for activation.

ananya.choudhary20@*.com · 
Right decision, I was writing you before to use MAS 
I have two laptops with Win 10 IoT Enterprise LTSC installed with MAS digital license.
I was entering this key in Parameters ans OS was accepting it. 
I got IID but couldn"t get CID. Yes, some bots were writing that the key was blocked.
But I really have no idea when it was blocked and actually if it was blocked when I found it.

MAS HWID Activation is using this key

QPM6N-7J2WJ-P88HH-P3YRH-VY74H

safe or not
but it worked 

At last i tried MAS HWID Activation 
it worked for me now system is activated with digital licensing 

Key blocked by Microsoft i checked it by myself not giving confirmation id . I installed on my laptop to check but not able to activate with this key

eenigma702@*.com  
Key is not a fake. I was checking it by entering it in Parameters and also using it to upgrade Win 10 Enterprise LTSC to IoT Enterprise.
Seems to me your bot is fake.

Key blocked not working