Have you tried rebooting after you apply settings? Also, are you sure you're on a legal/valid channel? Also, which build are you running?
Make sure you have ath2 disabled as well, since it's needed for DFS (I believe).
I use VHT 160 without any issues, so just wanted to check the basics first. _________________ Linksys WRT3200ACM r41586
- ExpressVPN | VAP & PBR | Synology NAS
Save button will write to the config and changes will take effect after reboot or you can try forcing with the apply button (which is not a replacement to save).