Hello Maciek Mucha,
Good to see you in Microsoft Community.
Firstly, could you let me know the specific system version? You can check it by pressing the Win key + R key, and typing "winver", then press Enter, please take a screenshot/photo of it, and only send the relevant information without PII in the next reply.
1. Run the Framework Repair Tool
You may visit Download Microsoft .NET Framework Repair Tool from Official Microsoft Download Center to download and run&install the "Microsoft .NET Framework Repair Tool", and follow the prompts. Then restart the system, and see if the program works.
2. Reinstall .Net Framework
Win + R to open "Run", type "optionalfeatures", press Enter to open the "Windows Features" interface, then check all items as shown in the image below, then press Enter*, and then the features will be installed (a network maybe required), and* restart the system*.*
If you have already checked these items, uncheck them, then save your settings, restart the system, and then recheck these entries in this interface to reinstall.
If the problem persists, can you provide me with the version of the program and its official link so I can help you check if this is a bug in the program itself?
If anything is unclear, please do not hesitate to let me know.
Best Regards,
Mosken_L - MSFT | Microsoft Community Support Specialist