Depending on the specific CM69 model, you may need to:

Many CM69 devices require a Factory Reset after the upgrade is complete to properly initialize new software parameters. Firmware Update Instructions Guide | PDF - Scribd

Use a high-quality USB drive or SD card formatted to FAT32 .

Flashing the wrong cm69-update.bin to a non-Compex or different SoC device will brick it. Always verify hardware revision and checksums.