Your best first step is to contact your local Omron representative. While they push customers toward their modern software (CX-One / CX-Programmer), they often have archives for legacy support. If you have a valid software license or a support contract, they may provide a link.
To resolve potential issues with Omron Syswin 3.4 64-bit, users can try the following: omron syswin 3.4 64 bit download