See this thread: https://discourse.osmc.tv/t/vero-4k-with-only-front-red-led-visible/
I had the exact same issue - the blue LED would flicker sometimes and sometimes it wouldn’t work at all.
I contacted support and they arranged to send out a replacement in exchange for my faulty one. Whilst the Vero 4K worked just fine, I’m a stickler for this stuff and if it was meant to work, then I like it to work…
Either way, I was extremely happy with @sam_nazarko and the support offered. I just made a backup of my faulty Vero 4K then restored it on the replacement and I was up and running in a matter of minutes.