Looks like it went splat part way though, either lost bluetooth/wifi or just fell flat on it's face for whatever reason.
Normally it's a case of going to a bike shop and get them to update it with the cable connection into the back of the display rather than via bluetooth/etube unless you know anyone with the shimano box/sm-pce1
Yes, it's a bummer that we can't download the updates as a file, then install via usb cable. OTA is the biggest potential danger when updating anything.
Same happened to me. Picked up my first eMTB today, charged up and tried updating the firmware, but it got interrupted due to weak wifi signal. Now it is bricked and only shows 'Shimano steps' logo for about 4 seconds then turns off. No chance to access PCE1. Need to book a service on Saturday.
I ended up borrowing PCE02 from the local bike store and re-flashed the firmware. Only took 5 minutes to fix it and now I am seriously considering purchasing PCE02 box.