My iPhone is not able to use WiFi 6 in Indonesia

Not entirely sure what you’re asking. Guessing this is Wi-Fi 6E?

Wi-Fi 6E should work just fine in the existing 2.4 and 5 GHz bands, with those clients supporting Wi-Fi 6E. (No present iPhone supports Wi-Fi 6E, though. Anywhere.)

Access to the 6 GHz band requires regulatory permission.

https://www.wi-fi.org/countries-enabling-wi-fi-in-6-ghz-wi-fi-6e

Approval from the Indonesian telecommunications regulators is needed.

Related Wi-Fi support details: iPhone Wi-Fi specification details - Apple Support

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Which device are you using? I can't do it on my iPhone 12 even after updating to iOS 17.4.

iPhone 13 Pro has 802.11ax worldwide, though available Wi-Fi channels will vary based on location.

Which router? Is its firmware current?

There is no “control channel” with Wi-Fi.

Do you have some other device (a Mac or PC) that can scan the local Wi-Fi network to confirm its settings?

Channel availability in Indonesia looks to be 32, 36, 40, 44, 48, 52, 56, 60, 64, and 68, and 149, 151, 153, 155, 157, 159, and 161. I’d try one of the last three top, though—if you’re in an area with lots of Wi-Fi networks—that’s all going to be jammed.

You’re probably going to need to discuss this with somebody locally too, unless somebody with Wi-Fi experience in your particular area happens to join this thread.

Tried on iphone 13 pro, ip 14 regular and 15 pro all working.

Try to reset Network Setting.

If that still dont work try to press volume up then volume down then hold power button until the phone restart and release when apple logo appear. (Do not Slide “Slide to Power off”

i did this on ip 14 and 13 pro. Both working fine. Now the iphone can scan 5Ghz only wifi along with 2.4Ghz. Hope it helps

Have you tried connecting the iPhone on a different Wi-Fi 6 network?

Configure a Wi-Fi scanner on the PC, and see what’s going on. (No, I don't have app recommendations, there.)

Iphones in indonesia can now connect to 5ghz wifi channel 32+ in iOS 17.4 bro after very long time at last

tried it while connected to telkoms*l

I think this is fixed in iOS 17.4 update. Give it a try. Same case as you but now i can connect to wifi6