I suggest to try it one more time with fresh install. I don't own this box but had situation when my box didn't boot. What I did:
- removed all partitions from SD card and created new fat32 partition and formatted the card with quick format
- installed libreelec with Rufus
Give it a try. If it won't work send back the box a take one that is confirmed 100% working.
Thx for the suggestion. I tried again and it was all the same