I may never play this game if this is not resolved. Tried about a year ago, gave up. Though I might give it another go, figured a solution should surely be around now.

Troubleshooting steps:
-Relaunched game
-Launched as admin
-Performed repair
-Performed ipconfig /flush dns, ipconfig /release, ipconfig /renew in admin cmd
-Restarted modem and router
-Restarted PC
-Tested wired and wireless connection
-Tried connecting through a VPN
-Uninstalled/Re-Installed (windows & game)
-Uninstalled/Re-Installed on different drive
-Cleared/deleted cache/ folders
-Opened port 3074
-Swapped DNS from cloudflare to google
-Reinstalled Battlenet launcher and game