I developed an app using Xamarin Forms and visual studio on macbook. When I tried to upload the app to App Store Connect, I get an error saying "Failed to parse altool outpoot: Failed to parse PList data type: Output: altool[5527:86472] Error:Error Could not find or load main class.  I hope you guys can help me figuring out this issue here. Thank you very much in advance!

I developed an app using Xamarin Forms and visual studio on macbook. When I tried to upload the app to App Store Connect, I get an error saying "Invalid toolchain. Your app was built with an unsupported SDK or version of Xcode. If you plan to submit this build to the App Store, make sure you are using the versions listed in "https://help.apple.com/xcode/mac/current/#/devf16aefe3b or later". I have tried to publish by using the latest xcode versions such as - Xcode 11.7, Xcode 12 beta 6 and Xcode 12 GM seed. But I am still getting the same error. I have to publish this app as soon as possible, I hope you guys can help me figuring out the issue here. Thank you very much in advance!