I started facing this annoying error after my UE4 started crashing for no reason.
When packaging I started getting this error with no information to track.
Cannot create SoftObjectPath with short package name ‘NoneNone’! You must pass in fully qualified package names
You can solve this by doing a stacktrace if you’re good with Visual Studio but here is a bruteforce/alternative way.
Step 1: Install Notepad++. This is free.
Step 2: In Notepad++, go to Search > Find In Files.
Step 3: 
Step 4: Search for ‘NoneNone’ as shown in the screenshot above.
Step 5: Hit Find All
Step 6: The number of results returned is the number of variables you have to fix. Result file will be a .uasset file and it will be encoded but there will be some clues here and there.
Step 7: Note the line number where the text ‘NoneNone’ is found.
Step 8: Copy 2 lines before and after the line that contains ‘NoneNone’. Example: if line 1536 contains ‘NoneNone’, then copy lines 1534 to 1538.
Step 9: Open a new file in Notepad++ and paste the lines you copied.
Step 10: Scroll to the right a little bit and you’ll see a bunch of variable names in every line. Problem lies in one of those variables. Note down these problem causing variable names.
Step 11: Close notepad++ and make sure you DO NOT save any changes (very important).
Step 12: Open UE4 and open the BP with the problem causing variable/variables, find the variable and make another variable just like it with a different name (same type, instance editable, expose on spawn etc…). DO NOT COPY the variable and paste. Recreate the variable manually.
Step 13: Now right click on the original variable and click ‘Find References’. This will show all the places you have used that variable. Replace every instance of that variable with the new one you created. [Note: You may have referenced the variable from other BPs in the project. Be sure to track the variable and change every occurrence. If you miss one or two occurrences, don’t worry it’ll come up in the build errors and you can fix it then]
Step 14: Do this for all the variables you saw in the Notepad file. It’ll be a tedious piece of work depending of how many variables died for whatever reason…
Step 15: Now go back to Notepad++, close all files and repeat step 2 to step 5. Rinse and repeat till there are no results.
Step 16: Retry packaging and it’ll package provided you don’t have any other problems.
Hopefully this will help anyone who is stuck. You don’t have to delete everything you created so far and restart. Reach out to me if you need assistance.