sirmilsolot Despite the wording of the error, this is usually caused by an antivirus blocking the game from starting. Even Windows Defender's Controlled Folder Access can have this effect. So please temporarily disable your AV and see whether it helps. If so, set exceptions for TS4_x64.exe and EADesktop.exe, plus TS4_DX9_x64 or TS4_x64_fpb if you're running the DirectX 9 or Memory Boost version of the game, respectively. More information about Defender and a couple other AVs is here:
https://crinrict.com/blog/2020/10/add-exceptions-to-anti-virus-programs.html
If this isn't the issue, please provide a dxdiag. Click Windows key-R, enter dxdiag in the run box, wait for the scan to finish, click "Save all information," and save the file to your desktop. From there, you can attach it to a reply using the paper clip (Attachment) icon included with the other formatting buttons.