The TS401 does not need to be registered and therefore you do not need any password.
An Autel ID is enough to get the updates.

The .bin (Firmware) and .aut  DTC lib) is all you need.
Ensure you select the correct device in the Maxilink software as the software is for more devices, not only the TS401.
And update allways BOTH, firmware and DTC. They have dependencies.

I have, from included CD if I remember right, the MaxiLink II Version 1.03 installed.

Select "TPMS" on the left side, then the "TS401" and I get the screen to select the Firmware (.bin) and DTC (.aut) files if use the "Select File" button.

I have never seen anything else and I do not have a TS301 or MaxiTire in my selection. Only TS101 and TS401
So I assume you have a wrong version of the update tool. I cannot tell you if there is one here on the download.
email to support@auteltech.com may help if you do not have the software on CD.

I have found a MaxiLink_290138144omh.zip on my  computer that seems to be the version I use.

You can dowload it from this URL if you do not find it here at Autel

http://www.fware.de/pub/MaxiLink_290138144omh.zip

 I also had a problem with update.  After update I no longer had access to vehicle types, and a message saying my .bin and .aut files were different.  The problem was that I only updated the .bin files and did not update the files described as DTC (.aut files).  I had new files and old files.  As soon as I went to the lower part of update screen (DTC) on desktop program and found the .aut files and downloaded into TS401 everything was right in the world once again.