Hi @Joe Barker is this a new web app? did you make any recent changes to your web app?
Hybrid Connection is supported in GA for Windows apps and Linux apps but not supported for Windows container apps. Also, keep in mind that App Service Hybrid Connection is only available in Basic, Standard, Premium, and Isolated and not Free pricing SKUs.
However you can try to add Hybrid Connections programmatically using the below CLI command. The commands provided operate at both the app and the App Service plan level. The app level commands are: az webapp hybrid-connection
Group az webapp hybrid-connection : Methods that list, add and remove hybrid-connections from webapps. This command group is in preview. It may be changed/removed in a future release. Commands: add : Add a hybrid-connection to a webapp. list : List the hybrid-connections on a webapp. remove : Remove a hybrid-connection from a webapp.
Hope that helps. Please let us know if you have further questions