why does xamarin suddenly not let me deploy to iOS devices
One reason this can happen is if you have multiple developer accounts set up in XCode. Here are the steps
- Verify that your device is on Apple member center
- Verify that your device is part of the relevant provisioning profile
- Repeat steps 1 and 2 for each account
- Create a new project in XCode and run it on the device. XCode may ask you to select the team (if you have multiple accounts)
- If you have multiple developer accounts (teams) set up in XCode, the repeat step 4 each time with a new project and select a different team each time.
These steps ensure that XCode clears the way for Xamarin. The idea is that Xamarin does not allow you to decide which "team" to use, so you want to make sure that XCode has done the setup for EVERY team.
I tripped over this one recently too.
The key is this part of the message:
Your application failed code-signing checks. Check your certificates, provisioning profiles, and bundle ids. Probably your device is not part of the selected provisioning profile
Likely, your provisioning profile has expired. The easiest way to solve this is to launch Xcode, create an empty project, and hit Run. This will go over a series of dialog boxes offering you to fix your provisioning profile until it deploys. Once this happens, you can switch back to Visual Studio/Xamarin Studio and deploy.