1. Clean DCS server installation. There is not necessary to uninstall and download-install again - just make 'cleanup' then 'repair'. Exactly cleanup then repair, not vice versa.
=> DONE
2. No any mods. Note: LoTATC, TacView etc. are mods despite they do not changes DCS binary files. I can remember at least 2 cases when some of these mods crashes DCS. Again - no any mods including mods is Saved Games.
=> Cleared savedgames but serversettings.lua
3. No any antiviruses, defenders etc. Disable them temporary.
=> None installed on the server
4. Browser type
=> Firefox 67.0.4, Google Chrome 75.0.3770.100
5. dcs.log, options.lua, serverSettings.lua, autoexec.cfg (if exists)
=> See attachments
6. Are there any errors in browser log (F12 in Chrome) when you try to connect?
=>Same error in both chrome and firefox
[b]localhost:8088/encryptedRequest:1 Failed to load resource: the server responded with a status of 422 (Unprocessable Entity)
index.html#/en/settings:1 Access to fetch at 'http://localhost:8088/encryptedRequest' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.[/b]
7. Disable all browser extentions.
=> None installed dcs.zip