Hi
I followed the instructions here: [OpenWrt Wiki] GL.iNet GL-AR750S (under " OEM easy installation").
And used the current release linked here (gl-ar750s-squashfs-sysupgrade.bin): Index of /releases/19.07.2/targets/ar71xx/generic/
The uploaded image file does not contain a supported format. Make sure that you choose the generic image format for your platform.
I also tried openwrt-ath79-nand-glinet_gl-ar750s-nor-nand-squashfs-sysupgrade.bin but received the same erorr.