If it worked fine prior to today, then there’s a very good chance that there is some sort of routing issue between your ISP and Blizzards ISP.
As far as “Your connection has been interrupted.” disconnects and lag, that is a dead giveaway that there is something wrong with the connection between your computer and the Battle.net servers. ~99% of the time, Blizzard is not to blame for lag and/or loss… And when they are, they will typically announce there are problems via the launcher, and via social media (Reddit, Twitter). The vast majority of the time, it’s usually a connection hop in between, an issue with the users internet service provider, or a problem on the users end that is to blame.
Diablo 2 (both the original game and Diablo II:Resurrected) has always been extremely sensitive to packet loss and excessive ping fluctuations. Even 1% packet loss will eventually result in the connection dropping. The higher the loss percentage and or the greater the ping fluctuations, the more frequent the dropouts happen.
It’s very likely a problematic internet hop between your service provider and Blizzards server. You could try switching regions in the Battle.net app just to see if it helps with the dropping connection issue. This isn’t a permanent solution, as the ping times will likely not be favorable…
If you want to investigate further, download winMTR:
Plug your regions IP into WinMTR and click Start. Let it run for a good 20 minutes.
Diablo II: Resurrected server IPs:
| Region | IP Address | 2nd IP Address |
|---|---|---|
| North America | 137.221.106.88 | 137.221.106.188 |
| Europe | 37.244.28.80 | 37.244.28.180 |
| Asia | 117.52.35.79 | 117.52.35.179 |
It will give a readout of all of the connection hops, as well as ping and packet loss information for each. The first hop being your router, the last hop being the start of Blizzards network. In between are the various connection hops the data travels between the two points.
There is an export log option in WinMTR, so you could forward the logs to your ISP’s support email, and they may be able to relay them to whatever hop may be having trouble so they can fix it.