Hi guys,
one of my shelly 2.5 is stuck and won't update firmware - still have ver 1.5.9 I bought it with that firmware. Im fighting with it for more then week and still no luck.
What I did:
-tried to update shelly via iPhone app
-tried to update shelly via ota update
-ota update with multiple old firmwares
-hard reset via app and switching power off and 5 clicks, then update
-switching cloud on and off, static ip etc.
No result at all, shelly is working fine, any ideas? 
Im having the same issue.
After no obvious tech support above. Im very surprised Shelly havent addressed this critical issue
So I found a fix...
1/ use a computer or mac.
join the wifi newtork of the shelly device you want to add.
2/ go to your browser and type http://192.168.33.1/
3/ refresh and wait. I may not join straight away.
4/ Goto internet > Client mode > input your wifi details there ..
5/ Then goto the shelly App on android or Iphone and refresh by dragging down the window, until you get discovered devices. press that
6/ Now look at the IP adress on the mobile screen!
7/ Go back to your PC and type in the Address in a browser
8/ when it loads, goto firmware update and wait 5 mins for it to update.
9/ Now back to the app and you can add.
repeat this for every shelly 2.5 until shelly fixes this
I'm experiencing similar difficulty trying to upgrade my Shelly 2.5 from v1.11.7 to v1.12.0 - the upgrade process appears to hang. Looking at a packet capture, the firmware download never begins except to retrieve metadata. The only indication that anything is meant to be happening is from http://shelly-ip/ota which shows status: "updating".
I've tried
- factory reset
- downloading the firmware .zip & updating the Shelly directly from a server on the same network
- upgrading to v1.11.8 via http://archive.shelly-tools.de/
The outcome seems to be the same every time.
My other Shelly 2.5 which shipped with v1.11.8 was able to upgrade to v1.12.0 with no problem.
For now v1.11.7 mostly works, but randomly (every ~6 hours on average) the device becomes "unavailable" to Home Assistant for about 45 seconds. I saw the same with the other Shelly 2.5 running v1.11.8 - I am trying to update them both to see if this issue has been mitigated 
EDIT: Tried again today & it updated instantly. No idea what changed, at least it's resolved fro now.
