# Unity error: type "x" exist in both 'A' and 'B'

I just opened a project made in unity version 2018.1.1f into Unity version 2020.1.1f I know opening the older projects is not supported by Unity but it opened fine.

The only problem is that it is giving an error which looks like this-

What I tried:

1. checking the script onetizationPlatform.cs to ensure nothing is wrong in it
2. checked that there's no two files with same name unitylifecyclemanager
3. doing point 2 with unityengine.advertisement.editor
4. deleting unityengine.advertisement.editor which caused another error so I had to restore it back
• While I haven't experienced this particular error myself, I have resolved similar errors after updates by checking the package manager and making sure all packages are up-to-date. Jan 3 at 5:36
• Is it possible UnityEngine.Advertisements.Editor used to be a standalone package and is now part of UnityEngine.Advertisements? (which would then conflict with the one still in your project). Since the latter has a higher version than the more specific one..? Jan 4 at 15:30
• I've had this problem before with some other package, and it was caused because I had installed package X manually, but it was also a dependency of some other package. So I had two versions of the same package. I solved it by removing the manually installed package and using the one that was the dependency. Jan 4 at 15:49
• Sorry but I didn't installed any package manually and also made sure that all of my packages are up to date Jan 4 at 16:01
• @D.Kallan Thanks mate! The problem is quite similar to mine,and maybe doing this will fix it. I'll update you about whatever happens Jan 5 at 13:36