Help: I can't enter the system interface after changing my Netgear SXS80 to RBS850 model

aip5

I changed the model of SXS80 to RBS850 in Telnet, and I wanted to flash the RBS850 firmware, but the firmware could not pass the verification and could not be flashed. Now the problem is,The firmware is still the original firmware,The machine can also operate normally,It can be used normally after connecting to the superior route,But the system management interface cannot be displayed,That is, there is no way to turn on the Telnet option to change back to the SXS80 model,At present, all firmware versions of SXK80 have no restrictions on the opening of Telnet,Just enter the /debug.html page to check it,But I can't enter the check now to open the Telnet option,I hope you help me, Teach me how to force Telnet on, thanks.