I just tried to update online my Volumio in raspberry pi zero with hifiberry dac and it now will not boot. I also tried to download new update to the sd card but that will not boot either. 
You are not alone . Look here.
wifi-connection-hotspot-after-july26-update-t12679.html
Hello
Thank you for the new version !!!
The new GUI looks fantastic !!!
I have also installed the update 2.598 on my old RPI 1 with a HifiBerry DAC. Unfortunately, something does not work.
The problem occurs both as an update and when I flash the SD card again. I have tried it with different SD cards with the same output.
The following is displayed on the connected screen: (see Foto)
On an RPI 2 and 3 with Allo BOSS, the update as well as the new flashing has worked without any problems.
I hope it helps with troubleshooting.
regards
rost21A
I have the same problem than rost21A, but with a Raspberry Pi 1B.
I have the same problem with my RaspberryPi 1, without anything else. I have to download 2.448 from this forum, without updating it.
Ok, will wait till your developer is back.
Same here on a Raspberry Pi 2 with HiFi Berry DAC.
Look forward to the new update.
Tried the latest version?
Yes, just tried. It is working now.
Thanks a lot.
k