start the game with no mods active and test add stellaris.exe to the exceptions list of your antivirus app ESPECIALLY if you have Windows Defender, add it to the Ransomware 'Apps Allowed Through' list. re-install game in Steam, run a Steam Verify when done. manually delete both the Steam/SteamApps/common/Stellaris AND Documents/Paradox/Stellaris folders move any valued save games elsewhere, and user_empire_designs.txt from /Documents/Paradox Interactive/Stellaris/ if you have made any custom empires or races. IF that doesn't help, Has the game ever run successfully on this computer? Or never? In the game launcher please set Display mode to Borderless.
Ok, that seems clear it is not a launcher issue.
