When I tries to pack/unpack a xnb file while without internet connection, I got a error message like this;
I think you should bring the issue to the developer of xnbcli: https://github.com/LeonBlade/xnbcli/issues
I opened an issue last night related to this. I thought rebuilding the program with Node.js would fix the issue. It turned out there was a minor bug with the code that prevented offline usage. Luckily, Leon Blade addressed this today and updated the source code. Unfortunately, he said he won't be making a major update until he has a solution for Stardew Valley 1.4, so if you want to unpack and repack xnb files offline, you'd need to build and run the source code with Node.Js. There's an instruction in the page to do that https://github.com/LeonBlade/xnbcli#developers Basically, you'd need to download and install Node.Js (my suggestion is you download V. 8.8.0 because that's what's working for me right now), Visual Studio Build Tools 2017 (if you're on Windows), and Python 2.7. The Visual Studio Build Tools is about 1.08GB. Then, after installing all of those, open Windows PowerShell as an admin (if you're on Windows) and change directory to where you unzipped/extracted the source code. By the way, make sure that Python 2.7 is in your environment path, meaning you can execute it directly on command line and PowerShell by typing the word "python" and pressing enter. Anyway, while in the directory containing the source code, run npm install. If all goes well, you'll now be able to unpack and repack xnb files using PowerShell or Command Line by typing npm run unpack or npm run pack. If you encounter any problem in building the app on Windows (Node.js is pretty buggy on Windows in my opinion) check out the issue that I posted last night https://github.com/LeonBlade/xnbcli/issues/17 Maybe it could help. By the way, it's a lot easier to do this on Linux, but if your SV is on Windows, then it's worth the hassle. Good luck.