Well DNS based blocking has its problems mainly devices bypassing your network defined DNS with some encrypted DNS(DoT,DoH) or using hardcoded custom DNS servers.
A. Device part of a business infrastructure:
Just don't change anything; those policy are there for a reason!
B. Consumer device:
1/ If we're talking about proprietary hardware/software forcing your network to use a specific DNS, then you need to provide more details because you should be able to change it.
2/ There is also the case for a malware:
A fresh start is preferable.
Disinfect the system while offline, then back up the needed files.
Reinstall the system on a new/old formatted drive.
With the exception of taking your privacy/security seriously this time.
Well DNS based blocking has its problems mainly devices bypassing your network defined DNS with some encrypted DNS(DoT,DoH) or using hardcoded custom DNS servers.
A. Device part of a business infrastructure:
Just don't change anything; those policy are there for a reason!
B. Consumer device:
1/ If we're talking about proprietary hardware/software forcing your network to use a specific DNS, then you need to provide more details because you should be able to change it.
2/ There is also the case for a malware:
A fresh start is preferable.
Disinfect the system while offline, then back up the needed files.
Reinstall the system on a new/old formatted drive.
With the exception of taking your privacy/security seriously this time.