I have built a iOS project with Unity and added a asset from the Unity Asset store called, Very Simple Ads. When I built the project in Unity, I had no errors, when I opened the project in xCode I have 12 errors. Which are "Apple Mach-O Linker" errors. Here is a screen shot of all the errors: SCREENSHOT
I know the errors are to do with the ads, but I am not for sure.
please make sure you have setup import settings for plugin correct and check iOS platform checkbox. Currently, the problem is your plugin did not exported right and linker can't find listed methods.
Please read more information about plugin import settings here https://docs.unity3d.com/Manual/PluginInspector.html
When you export via unity to xcode you have to put frameworks for ios from the screenshot i came to now tat you have integrated google mobile ads so you need to add google mobile ads framework to your xcode project
you can do so by simply going to project setting general and scroll down to frameworks use the small "+" sign at the end of the frameworks to add the frameworks or simply drag the downloaded framework to the hirarchy of your project in frameworks folder
You can download google mobile ads framework from the link below https://firebase.google.com/docs/admob/ios/download
Regards
