Here's my test of using the Ubuntu remot3it_register on my test system. Since this device doesn't have an "eth0" device, the SERVICEBASENAME is just blank and there's an error message looking for eth0 as you can see.
The version of the wevedconnectd installer I'm using is: Version: 1.3-07j-x86
However, it did work for me. What's different about what you are doing?
Try editing the /usr/bin/remot3it_register and change this line:
and try again. You are apparently not getting a login token, which is pretty strange if the weavedinstaller is able to do so, as they use the exact same library functions for login.
The only thing I can think of, which I encountered myself, is that if your password includes a special character such as $, then it may be necessary to escape it using \ so that it is interpreted literally. However that only applies to putting your credentials directly in the script.
gary@gary-S551LA:~$ sudo remot3it_register
remot3.it connection installer Version: v1.3-07_x86_OEM lib_v1.3-07_x86
Modified: February 01, 2017 (library) February 01, 2017
Platform = i686
Please enter your remot3.it Username (e-mail address):
Please enter your remot3.it password:
eth0: error fetching interface information: Device not found
Serial = -45ldhC8MlK0QReIUuGkZ