on 19.7 can't install waiting for backend

[progl]

Hi all
I have proxmox 6, upgraded from 5, on in container with opensense working normaly.

Now I want to upgrade from full new image(dvd) and stucked - when i login with installer on this or another container system shows 'waiting for backend' and no more. Saw here the same issue but didn't understand what to do.
Please help me.

[progl]

found reason - unplugged all usb devices and restarated