@RaghuGG1 
sounds like a compatibility issue between the iPhone 16 Pro and the Deco XE75 Pro's 6GHz WiFi. Some devices have limitations on 6GHz band support depending on region settings or firmware restrictions. Try checking if WiFi 6E is enabled on your iPhone and ensure that the Deco XE75 Pro is set to WPA3 security (since some Apple devices require it for 6GHz connections). Also, updating both the router firmware and iPhone software might help.