Sorry you are having trouble with this. It looks like the updater’s file download is failing. I’ve seen this fail before when the storage on an AmpliPi gets full.
The simplest way to get to a newer release is to re-image your AmpliPi with 0.2.1 and upgrade to 0.3.0 from there.
Follow the steps to re-image here: Re-imaging the Raspberry Pi - #3 by Lohrer
If you wait a day or so there will be a 0.3.0 image available to make this process a bit simpler.
I hope this helps,
Lincoln