Ensure you are not trying to install an ap3g1 image on an ap3g2 device; they are not compatible.
.tar (Archive containing the image and HTML management files) 🚀 Why Use This Specific Version? Ap3g2-k9w7-tar.153-3.jd.tar- Download
Disable your Windows Firewall or any antivirus software that might block the TFTP port (69). Ensure you are not trying to install an