Unable to batch import for creating .package file

Hey all,

Not sure if this is the right place to post, but i need help! I'm very new to all of this so please be patient with me lol

I've run into a problem when creating a package file.

So I "create empty package file" under the tools tab , when it takes me to the other screen, I click on "batch import" (this is where i get the error)

The Sims 4 Studio - Version 3.1.5.4

System.NullReferenceException: Object reference not set to an instance of an object.

at S4Studio.ViewModels.Warehouse.WarehouseResourceClassMap.GetResourceInstance(IResourceKey key)

at S4Studio.ViewModels.Warehouse.WarehousePackageViewModel.BatchImport(IEnumerable`1 filepaths)


The thing is i've  followed the above steps before, created/saved 3 package files prior without any errors but when I tried the last one(editing club rules) it started with that above error. I even went back and re-create a previous one and i'm now getting that error on all previous ones(when using batch import). 

I've restarted my computer, downloaded the latest version of S4S(I had 3.1.5.3 before), checked my anti-virus. 

Not sure what else to do, I checked other forums but couldnt find anything there.

Thanks in advance.
-M