Hello DHyyc,
You came from this resource, which is related to your issue connecting your wireless headphones to your iPhone: If you can't connect a Bluetooth accessory to your iPhone or iPad
If you were unable to resolve the issue with those steps, then you'll need to isolate the issue further. Do other Bluetooth devices connect with your iPhone 12? Do they show up as discoverable? When you go to Settings > Bluetooth on your iPhone, is it greyed/dimmed out? What happens if you test the wireless headphones with other devices? Do they connect and work as expected?
If the issue only occurs with these wireless headphones, then you may need to contact the manufacturer of the product for support. In the US, you can contact Sony Support here: Support for Sony products | Sony USA
Let us know how it goes.
Take care.