Hi Paul.
Starting with the time being off, your IoTaWatt is configured to UTC (GMT). There is no local time offset. You would need to set that in the Setup/Device section.
The log you posted shows that the EmonCMS posting is about 15 hours behind, but as you say, logging locally OK.
Can you try removing the userid field in your server settings to change to unencrypted posting? If that resolves the backlog, change back and see if it stops again.
If that doesn’t resolve the problem, please post the log back to the power fail that you mention.
Update: There appear to be some ongoing problems with Emoncms that may be causing this. The symptoms appear to be consistent with what you are reporting… Emoncms accepts the data but then doesn’t post it. That would explain the lack of communications errors in your log, and why your IoTaWatt is serving you locally while unable to post remotely. Hopefully, the data is in a backlog queue and will be posted when the problem is resolved, but maybe not. To be on the safe side, I’d recommend stopping your Emoncms server (server=NONE) and restarting when the problem has been resolved. You can follow that issue in this post: 5 hours of no updating of Feeds