In the game launcher please set Display mode to Borderless.
IF that doesn't help, Install ALL these Microsoft modules:
www.microsoft.com
www.microsoft.com
This update is the latest in a cumulative series of feature additions and bug fixes for Microsoft Visual C++ 2015 Redistributable.
www.microsoft.com
The Microsoft DirectX® End-User Runtime installs a number of runtime libraries from the legacy DirectX SDK for some games that use D3DX9, D3DX10, D3DX11, XAudio 2.7, XInput 1.3, XACT, and/or Managed DirectX 1.1. Note that this package does not modify the DirectX Runtime installed on your Windows...
www.microsoft.com
(run dxsetup.exe after extracting from this download)
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.
Also if you have FRAPS or the MSI Gaming App or Rivatuner installed, disable it as it clashes with this game.
If that doesn't help:
DXDIAG is a program you run from a command prompt or the Windows start menu 'run' dialog box (or 'search programs' in Windows 7 or later). After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.
Please attach your Documents/Paradox/Stellaris/settings.txt and pdx_settings.txt .
From your Documents/Paradox/Stellaris/logs/ folder, attach system.log , error.log .