Agree with the advice given here about reset but a couple of things first,I have not a done a factory reset ever. Is that the next step?
First, are you using the Asus App on your phone? Wondering about that power level and if you possibly did something by mistake. I'd get rid of the app on the phone and only work from the windows pc and web browser.
Lets rule that out first, login to the gui from the web browser, go to your wifi settings, then the professional tab. In the drop down pick the 5.0 band then scroll all the way to the bottom of the page and check the power level. I'd crank it all the way up for these purposes. APPLY, then do the same with 2.4. IF you made any changes do a quick reboot and check the clients in the wifi network map, view list and see if they changed to 866 (not 433).
If the power levels were fine and you didn't change anything, then I would reset the router back to factory...
Easy way first is gui reset.
- First make sure you have any ISP settings you may need.
- Administration, Restore/Save/Upload, Factory Default (CHECK initialize all settings), Then click restore button. When that finishes it will come up to the setup wizard. Your laptop may or may not have a wifi connection and you may need to connect to the default Asus wifi to begin; look for a network "Asus xxxxx" I've seen Asus2.4 and Asus90.
Nuke option.
-https://www.asus.com/support/FAQ/1000925/
With either reset option, I'd use the factory defaults from the start. Check the network list and see if they show 866 and two streams. If you only did the gui reset and it still shows 433 go ahead and do the nuke option. If it still shows 433 after that, I think it's time to upgrade to a new router.
Let us know...good luck.