I had it happen today. Before that, after the last patch, I had problems. The game said that it was not possible to log in, I restarted the computer and everything worked. But two hours ago, everything broke down. I tried this method, but it didn't help.
Since you don't have a great internet connection, simply run a "slow" DCS repair.
If this doesn't fix the issue:
Delete this folder: "\DCS World OpenBeta\CoreMods\aircraft\ChinaAssetPack" (you'll have to re-download about 5 GB of data).
Then run another "slow" DCS repair.
Since you don't have a great internet connection, simply run a "slow" DCS repair.
What should I do?