Can you explain better when you say that it doesn't work anymore? Do the LEDs light up when you plug in the power?
Did it suddenly stop working or did it stop working after trying to roll back to the original firmware?
Can you assign static IP on your PC and try to ping the router? Use 192.168.1.10/255.255.255.0 and try to ping 192.168.1.1 which is the default Openwrt IP.
If you had assigned a different IP, assign to PC accordingly and try to ping it.
If you remember the default IP that the original firmware had, also try that one.
Yes, try to login now with SSH, user root and your password.
Should you be able to login and see the Openwrt welcome screen, enter the command firstboot to restore factory defaults, reboot and try once again to upgrade the original firmware.
I cannot find much information about this device. From one hand it is discontinued and from the other hand it has low specs so it will not have much of support.
Try generic methods for upgrading with TFTP during boot, in case you get lucky.