“Error updating data” isn’t your connection. It’s a 20 second timeout in the client, and here’s how I got around it.

Spent most of today on this so hopefully it saves someone else the trouble.

Symptom: Steam updates fine, you launch, it starts pulling the extra data, and then it dies with "Error updating data: please check your connection and try again". You hit retry. A little bit downloads. It dies again. The remaining total drops a tiny amount each time and then just stops moving. Mine sat at 1.34 GB for two days no matter how many times I retried.

I checked everything the internet tells you to check. DNS, IPv6, MTU, firewall, disk space, verify files, wipe the download cache. None of it helped, because the problem isn't on your end.

What's actually happening

The client gives each file 20 seconds to download, and it starts about 100 downloads at the same time. If your connection isn't fast, each of those 100 gets a sliver of your bandwidth and can't finish in 20 seconds, so it gets killed. And then, this is the part that makes it unfixable, the failed download starts over from zero instead of picking up where it left off. So you retry, it re-downloads the same bytes, and it dies at the same spot. Forever.

You can see it in your own log. Look for a line like this:

General priority download latency (ms): Min 0.00, Max 20,000.40, ... Request count 101

That Max is exactly 20,000 ms every single time. That's the timeout. And file size barely matters. I had a 1.9 MB file fail in the same batch as a 92 MB one, because with 100 downloads competing even small files run out of clock.

The workaround

The CDN itself is completely fine, I tested it. So you can just download the files yourself with something that doesn't have a stupid timeout, and drop them where the client expects them.

Your log lives here:

• Windows: %USERPROFILE%\AppData\LocalLow\Wizards Of The Coast\MTGA\Player.log
• Linux/Steam Proton: ~/.local/share/Steam/steamapps/compatdata/2141910/pfx/drive_c/users/steamuser/AppData/LocalLow/Wizards Of The Coast/MTGA/Player.log

Open it and search for assets.mtgarena.wizards.com. Every failed download logs its full URL. Grab all of them, feed them to whatever download manager you like (I used aria2c, anything that resumes works), and let them finish. Took me about four minutes, at the exact same speed the client was failing at.

Then drop the files into MTGA_Data/Downloads inside your game folder, in the right subfolder. .pck files go in Audio/, Manifest_*.mtga go in the root of Downloads/, Raw_* files go in Raw/. Keep the filenames exactly as they are, the hash in the name is how the client identifies them. Launch, it checks them, moves on.

You may have to do this twice. The client only logs the URLs it actually tried, so the next launch reveals the next batch. Second round was small for me and then it was done. Happy to paste the exact commands in the comments if anyone wants them.

Before anyone says it: no, this isn't a Linux thing. I play through Proton, which is why I had the tools to dig into it, but the timeout and the concurrency are in the client's own code. Anyone on Windows with similar bandwidth is hitting the same wall, they just have no way to see why.

I've filed a support ticket with the full log and commented on the existing UserVoice threads. If you're affected go vote, because the fix is pretty simple on their end: make downloads resumable, or time out based on whether data is actually arriving instead of a flat 20 seconds.

The really annoying part is that error message. "Check your connection" sends everyone chasing a problem that doesn't exist, on hardware they can't fix, while the actual bug sits in the downloader.

Small note: English isn't my first language, so I used AI to help me write this up cleanly. The diagnosis, the logs and the testing are all mine. I just didn't want the language getting in the way of the information.