ultra 2 after upgrade to os 6.1.7 can't access frontview

dear all,

i would like to kindly ask you for your help.

i tried to search all forums, but i do not find any solutions for my issue.

i upgraded from os 4 to os 6 (6.1.7) and everything ran flawlessly, until i forgot, that i can't run apt-get update && apt-get upgrade.

after i restarted nasdisk, i can't access frontview. i tried to reinstall os (also formatted hdd) with no success, i tried to reset nasdisk to default factory settings, but again, i can't redirect to frontview.
also i tried to to recover nasdisk from usb - but nasdisk didn't accept any of my usb drive, and process didn't start.

when i'm checking naskdis through radiar - nasdisk is green and i don't have any comments in the right column, but when i click on "setup" button i see "Firefox can't establish a connection to the server at ..."

samba is running, i see folders in windows and linux. when i want to discover nasdisk through readycloud.netgear.com i am able to discover it, but can redirect to front view - i have got same error "Firefox ...."

when i connect to nasdisk through telnet and write "find / -type d -name 'frontview'" there is no directory named frontview.

please, is there any chance to recover my nasdisk and access frontview to manage it?

thank you for your help.