AR-750S Bricked! Loaded wrong uboot

Hello

I accidentally loaded wrong uboot binary (uboot-gl-ar750-20180705-md5-447252d5073b4cdb5fa53252010a876a.bin) instead of openwrt-ar750s-3.215-0921-1663732520.img, now device does not boot. Center LED is lit. Recovery reset (hold reset, power on, wait for 5 blinks) is not working, only center LED stays lit, no blinking happens

Any help greatly appreciated.
Thanks so much

Whats the output of Serial TTL UART?

As using serial might be the only way to get it working again.

What version of USB-UART cable should I use 3.3V or 5V?
This page does not specify the voltage level information
Thanks

If you used the wrong uboot, then it is bricked and the only way is to desolder and reprogram the flash.

Can it be reflashed using serial cable?
What is the UART voltage level 3.3V or 5V?

Thanks

If you have taken out uboot serial TTL will not save you, only desoldering the NOR/NAND chip and reprogramming it that way will solve your issue.