A rather stupid error without any indication on what’s wrong. The button Allow always and Allow doesnt work for “Code sign wants to sign using key”. You can press it but does not do anything and the system doesn’t say not allowed or some sort. This happened when I deployed from Visual Studio using Xamarin to iPhone device through the mac I had to verify the certificate but I couldn’t.
Source of the solution: https://forums.developer.apple.com/thread/25092
“I am using a software to make the movement of my mouse smoother. The app is called “SmoothMouse” and if it is active, it’s impossible to click prompt asked by the keychain. I deactivated it and everything worked fine. So, if you use VPN or any software that simulate/modify your mouse position, keychain won’t let you click on it’s popup messages.”
My issue came from using Teamviewer to remote control the mac and doing everything from Teamviewer. After I went on the local machine, closed down Teamviewer. Deployed the solution from Visual Studio, got the “Code sign wants to sign using key” message on the mac and press with the local mouse I was allow to press the buttons. Hurray! What a stupid issue.