Hi Peg, I don't have the manual any more - so sorry about that. They don't have a web interface - they don't even get assigned an IP address. If holding down the reset button for 30 seconds doesn't work, I think it's likely the unit is broken. There are some tools which will analyse your powerline network - but they're for advanced technical diagnosis. Take a look at https://github.com/qca/open-plc-utils/
Good luck!