I have a similar issue. My fresh Battle.net installer cannot connect to the update service.
Here’s an excerpt from C:\ProgramData\Battle.net\Setup\bna_2\Logs\battle.net-setup.log
Downloader - {2520} INF: adding network address 37.244.28.30:1119 for server http://eu.patch.battle.net:1119
(The next two lines were repeated five times)
Downloader - {2520} ERR (d:\buildserver\bna-3\work-git\bootstrapper-repository\contrib\contrib\bnl_dl2\net\source\net\standardsocketnetwork.cpp, line 650): error receiving data from socket descriptor 1216: [10054]
Network - {2520} ERR (d:\buildserver\bna-3\work-git\bootstrapper-repository\contrib\contrib\bnl_dl2\net\source\net\standardnetworkimpl.cpp, line 1087): failed to receive data from socket: NET_ERR_CONNECTION_RESET
Downloader - {2520} INF: fetch limit exceeded for download ID 1 (5/5 attempts)
Downloader - {2520} ERR (d:\buildserver\bna-3\work-git\bootstrapper-repository\contrib\contrib\bnl_dl2\downloader\source\downloader\standarddownloaderimpl.cpp, line 977): failing download ID 1: fetch limit exceeded
Download error - DOWNLOAD_ERR_NOT_AVAILABLE
Failed to download versions file
Both 37.244.28.30 and eu.patch.battle.net
are pingable, although the latter is resolved and pinged over IPv6.
I’ve deleted everything before reinstalling Battle net.
UPDATE: That error was happened on 5G T-Mobile in Germany. It disappeared on the Vodafone cable connection.