Why am I not able to login using the default password ?

As of January 1st 2020, Lantronix was required by the state of California to make a password change per unit.

Here is an article talking about this: https://www.hwglaw.com/compliance-planning-for-california-iot-security-requirements/

The new law stated that as of January 1st all units must have a unique password. So due to the requirements by the state of California, (where Lantronix is based,) each unit has a unique password.

Due to the limited size on the product the Device ID could not be added, so it has been incorporated into the 2D Bar-code on the unit.

The 2-Dimension Bar-code needs to be scanned with a bar code reading software that can be downloaded onto a phone from (Google play or the iTunes store,) and then scan the barcode.

After the (S2) you will find a string of 32 characters. The last 8 digits are to be used as the Password to the device.

Username will be as mentioned in the User Guide respectively
Password : (Last 8 Digits of the Device-ID from bar code scan)

Example: (V1)1(C1)7(P1)XDT2321002-01(R1)C12(D1)20W13(L1)THAILAND 02(S1)xxxxxxxxxxxx(S2)xxxxxxxxxxxxxxxxxxxxxxXXXXXXXX(M1)xxxxxxxxxxxx(E1).  

There is also a secondary option to know the Device-ID i.e., by Logging in through Telnet.

The Device-ID would be available right in the Banner information of the Login page.

You can just use the Last 8-digits from it to log in to the device as shown above from the 32 available characters.

It is highly recommended by Lantronix to change the password as soon as you log into the device as a best practice.