Factory defaults on Ericsson BB set the LMT ethernet port to be reachable at 169.254.2.2 with your computer at 169.254.2.1
Before you start you have to be able to ping it from your PC.
Now, you said you were able to contact initially with the BB. Here’s the interesting part on what probably happened to you:
New Ericsson BB software has a limitation: before you install your script (with the production software of your network) you have to make sure the NL (network loader or bootloader) version of your BB hardware is at least L19Q1.
If you install a new software without that NL the BB will crash after the first restart. The button ‘Integrate’ will not be usable.
Also, the BB with not bring up its ethernet connection, and you will not be able to connect to it, even ping will not work as the interface does not get up. Evidently you will not be able to connect to it via moshell.
You say you installed a script, probably the autointegration xml with basic cv and software. If that’s the case then the BB cannot be restored to default settings because you cannot connect to it via ETH.
The reset button does not work either, it does not set factory defaults and the BB stays with ETH dead.
I don’t know if there’s a console cable pinout for these, or if setting a DHCP server might bring the ETH up. I haven’t had time to test it with a network sniffer.