In the past, staff has said they are not interested in doing alternative update methods.
Let me guess, you probably have a Static IP address set in the hub? Typically if your connection isn't set up correctly, this update failure happens. Try switching to DHCP in the Hubitat hub and reserving the address in your router instead.
One of two things. Your DNS is not correct under static ip settings as @neonturbo points out or under settings>>network setup your ethernet speed is not set to auto. Check both of those.
I would set your hub to DHCP and use a reservation in the router instead.
Sorry I was involve in a lot of things here guys....
My hub ip is working with DHCP and I indeed it use an ip reservation on my router.
My DNS is automatically assigned by my ISP to my router.
The rare is the gub always started to download up to about 8% and then fail..... it looks like is not doing a RESUME with the download process?
And another clue is I always updated without any problem... until now.
under settings>>network setup make sure that network speed is set to auto. If so I would hit the network reset button on the bottom of the hub. Use a toothpick or paperclip and press for 7 seconds. It is the only round hole out of all the square ones.
Well... after made all those procedures I unfortunately have to say the result was the same.
I put the HE in another subnet, behing a VPN, without VPN, I reset the network as instructed by [rlithgow1], I made a soft reset... and nothing.. same result of "Download Failed"
One thing I noticed indeed and is it looks in one of those tryouts the download finished because the Hub said something like "checking the downloaded file" or similar... but at the end it report that download was not good either.....
I'm trying to update:
Currently running version: 2.3.4.129
New version available: 2.3.4.150
Try using the diagnostics tool on port 8081 to download latest firmware then use the previous version button to switch to the new version. This may get around whatever issue the regular UI is having.