@Marvin_S Thank you for your reply.

> Did you upgrade firmware via web interface of the router on a computer?  

Yes, via web interface.

>Please verify the country code and hardware version of your router before upgrading, ensure you choose the correct firmware to install on your device.

My router is "MR400(EU) Ver:3.0".

So I choose a firmware "Archer MR400(EU) V2/V3      LTE_GATEWAY_20200325".

> If it is a special and customized hardware that was developed for the local Service Providers, you cannot install the generic firmware on it.

How do I check above?

@Marvin_S 

> I want to use LTE band selection fuction with MR400 v3.

> https://community.tp-link.com/en/home/forum/topic/241534

I want to use the LTE band selection function, so I obtained the firmware from the URL above.

@Marvin_S @Motoki 

I've noticed a post from about three weeks ago describing the same error I'm encountering, but it seems the issue remains unresolved. I'm posting this to both seek a solution and to bring renewed attention to the problem.

## My situation:
1. I'm trying to update the firmware on my MR400 router.
2. I'm encountering the same error as described in the post from three weeks ago.
3. The update process is failing, and I'm unable to proceed.

## Questions:
1. Has anyone found a solution to this issue since the original post?
2. Are there any troubleshooting steps I can try to resolve this?
3. I've seen information about using TFTP for updates on the MR200, but I couldn't find similar instructions for the MR400. Would anyone be able to provide guidance on using TFTP to update the MR400 firmware?

Any help or advice would be greatly appreciated. Thank you in advance for your time and assistance!