Take a look at the Cohesive Networks Documentation site for all information related to your VNS3 Network Platform (VNS3, VNS3:ms, and the CNVPN client).  Specific VNS3 Troubleshooting Documentation is available on the Documentation Site.

IPsec troubleshooting can typically be resolved by ensureing both sides of a tunnel are using exactly the same parameters.  Cohesive Networks always recommends filling out the VNS3 Support Checklist Spreadsheet or similar when planing and negotiating IPsec tunnels.