Why I’m having trouble to connect wifi 6GHz I checked google it’s said that iPhone 13 Pro Max support 6ghz

You have an iPhone13 Pro Max, which supports Wi-Fi 6, not Wi-Fi 6E.

Wi-Fi 6 GHz support requires Wi-Fi 6E or (standardization imminent) Wi-Fi 7.

iPhone 13 Pro Max - Technical Specifications - Apple Support

While you do have mmWave (sub 6 GHz) for 5G cellular (green), you do not have Wi-Fi 6E; no 6 GHz for Wi-Fi (red).

CBOB_ wrote:

So your going to want to get the iPhone 16 because I can’t help with this situation

Per Apple, “iPhone 15 Pro, iPhone 15 Pro Max, iPhone 16 (all models), or later” support Wi-Fi 6E 6 GHz: Use Wi-Fi 6E networks with Apple devices - Apple Support

Wifi 6 only operates in the 2.4 GHz and 5GHz bands. You need a wifi 6E router to operate in the 6GHz band.

Sorry but I'm not familiar with that particular modem. I did a quick search for it but didn't find a match.

As for your iPhone 13 Pro Max, the specs shown here, under Cellular and Wireless, says it only supports wifi 6.

Perhaps a call or a visit to the Genius Bar at an Apple Store could offer some additional clarification.

So your going to want to get the iPhone 16 because I can’t help with this situation