The Endel Quick Access feature cannot be used on LinkBuds (WF-L900) even after completing all the settings in the Sony | Headphones Connect app.
In addition to the settings on the Sony | Headphones Connect app, you need to install and complete the settings on the Endel app.
Once the settings on the Service tab using the Sony | Headphones Connect app have been completed, install and open the Endel app and complete the settings to allow a Bluetooth connection to the headphones.