I've seen a few posts on similar themes. My Hub 3 light is always red and has been for a few weeks. It's running at a reasonable temperature and the connection is good, but other posts seem to suggest the Hub may need replacing. I've restarted/rebooted several times, but nothing changes.
I tried to raise this via the on-line chat and was told that there was a network issue in my area, which would be resolved yesterday and my Hub would return to normal operation. It hasn't! I was also told that I was due a refund due to the service disruption (although generally the connection has been good).