Legitimate SolidWorks checks in with Dassault’s servers periodically. If a pirated key generator (keygen) was used, the software will eventually fail the online check and revert to "0 days remaining." By blocking the domain, the software cannot verify that the key is fake.
The "SolidWorks Hosts File" Trick: Solving Connection Lag and License Gremlins Solidworks Host File Block
If you have a legitimate license or want to clean your system: Solidworks Host File Block
Add entries at the bottom (example):