this is the link http://downloads.openwrt.org/releases/21.02.0/targets/mvebu/cortexa9/openwrt-21.02.0-mvebu-cortexa9-linksys_wrt1900acs-squashfs-factory.img
also when i try to use the upgrade image for my router i get this error instead
the link to the upgrade image is this http://downloads.openwrt.org/releases/21.02.0/targets/mvebu/cortexa9/openwrt-21.02.0-mvebu-cortexa9-linksys_wrt1900acs-squashfs-sysupgrade.bin