Have you tried restarting your computer?
Also, have you already connected as many Bluetooth items to your computer as it can handle at once? (ie. do you have a Bluetooth mouse and keyboard using all the computer’s Bluetooth capability that is preventing any new devices connecting?)

Not sure if that’s still how Bluetooth works, or just on older computers but might that be the issue…?

I have tryed all of that my Bose headphones working just good with same computer with bluetooth so

it´s have to be something with Sonos ace headphones.

It would help if you gave the following info about your computer:

• OS
• Model #

Other points you should be aware of regarding the Ace:

• Note: When you turn on your headphones, they automatically connect to the most recently connected Bluetooth device, if available. 

If Necessary Factory reset (however this step should not be required)

• If you want to set up your Sonos Ace like new, you can factory reset your product to clear all of its settings and previously paired Bluetooth devices.
• Make sure your Sonos Ace is powered on.
• Press and hold the Power/Bluetooth button.
• While holding, plug your Sonos Ace into power.

• The status light will flash white when your headphones have been reset. 

  Note: Sonos Ace is immediately ready to pair with a Bluetooth device when unboxed and after a factory reset.

EDIT: No offense intended...but you were very emphatic about the Ace being in paring mode which means the LED on the Left Cup was Blinking Blue...correct?

Thx I have tried all of that,

The computer is PC windows, it´s bliking blue and I have reset the product. Even close down my android phone, It was no problem to conect ace to to the phone. So I have delet everything and start from the beginning and the computer still cant find my ace.

Once again...what model is your PC? 

Such as HP Model XXXX

It´s Dell Alienware aurora Ryzen edition, whats that have to do with Bluethoo problem with Sonos ace when all other products have no problems even other Sonos products?

I notice that my PC is often paired, but not connected. I must go to the PC’s settings and force the PC to connect.

Hi Buzz,

and how do you force your PC to conecet when the PC cant find the Ace headphones?

Here are things you can try/check:

Make sure that other BT devices can connect 

Check if there is an update for the BT Stack drivers . You’ll Probably have go to the online support page for your PC

Check in BT settings to see if the PC is asking for permission to connect to Ace

Depending on your Windows Desktop setup, you may have a permanent search field or you can simultaneously press the Windows key and ‘s’, Enter “Bluetooth” here. I sometimes see that my PC is paired, but not connected and I must manually connect.

Thx Buzz you made my day ;-)

I have to force connection every time...