EX4100 not uploading the firmware from Safe Mode recovery page

Hi,
I was trying to revert from OS5 to OS3 and I used the command below in ssh:
dd if=/dev/zero of=/dev/mtdblock1

Unfortunatly, after reboot, the screen was showing no firmware found!, so I tried to access the ip address through browser and upload the firmware from the “Safe Mode” recovery page with no luck, it’s keep looping without any percentage indication (i tried chrome, edge, ie, firefox with no luck).

Note, I bought this device as used one, so there is no warranty.

any help please?

Thanks for your reply, unfortunately nothing is working except the safe mode. and if i tried to upload the firmware and hit apply button it keeps looping with no response.