Orange light usually means that the bootloader didn't find anything usable in the flash and is hence falling back to TFTP.
This can happen if you have flashed non-UBI sysupgrade image on a device which uses UBI or in any other way managed to kill even the recovery image stored in flash (not to be confused with failsafe mode, the recovery image allows to dual-boot into initramfs to flash or fix things in case the production image has been broken).
failsafe mode is not available at this point, as OpenWrt has not been loaded (the Orange LED would be off and white LED would be flashing).
So you will need to setup a TFTP server connected to a LAN port of the device listening on IP 192.168.1.254/24, it should serve the file openwrt-mediatek-mt7622-linksys_e8450-ubi-initramfs-recovery.itb which the router will request, write to the flash (so you have a working recovery image again) and then start it. From there, please upload and flash openwrt-mediatek-mt7622-linksys_e8450-ubi-squashfs-sysupgrade.itb.
Let me know how it goes 