Correlator3D is signed with a digital certificate from the third-party certificate authority SSL. Computers that do not have a live internet connection might not be able to download the updated certificate authority list and this can cause the invalid digital signature error.
To resolve this:
1) Download the latest SSL Security Certificates here.
2) Unzip the four certificate files (.crt).
3) Right-click on the first certificate file and select Install Certificate.
4) Follow the steps of the Certificate Import Wizard.
5) Repeat steps 3 and 4 for the three other certificates.
6) Install Correlator3D.