ClamAV does no longer update its signatures. Even starting freshclam.exe manually fails.
One source which may cause this problem are the ClamAV mirror servers. To solve the problem, please delete the following file:
Another problem might be caused by the Windows Defender. Add the following paths to the exclusions:C:\ProgramData\JAM Software\ClamAVInABox\SignaturesC:\Program Files (x86)\Common Files\JAMSoftware\ClamAVInABox\sanesecuritydbtemp