No matching function for call to "NSStringFromIl2CppString' in Unity IOS XCode build

I have been getting this error whenever I build my game in xcode. They are all produced by UnityMonetizationPurchasingAdapter.mm file. I have waited for Unity Ads SDK 3.4.2 as the developers said I should in another thread, but the 'fix' did not stop these errors. I have heard it has something to do with re importing the .mm files, but I don't know how to do that. I am at a roadblock in my development as I cannot physically test my game, please help!

 

re importing still doesn't work for me.
Tried UnityAds.framework and separated m+mm files.
Tried to add as a group, relative to the project or to the group. Recursive or non-recursive.
Still no luck.

There's already similar thread where Unity promised to fix it in 3.4.2
https://forum.unity.com/threads/no-...ystring-and-_nsstringfromil2cppstring.804555/