I see! As you can play in Modded realm this does indicate an EAC-related issue, as EAC only applies to Official realm.
Are any specific error messages shown on screen? As this can help in narrowing down the appropriate solution.
If not, I would recommend to start with the following -
- Repair Easy Anti-Cheat
- Add Anti-Virus and Firewall exceptions for both Vermintide 2 and Easy Anti-Cheat
- Perform a ‘Selective Startup’ which can help determine if a background application is the cause
Please see: