These codecs are 32-bit only (most of them are old Video for Windows codecs): a 64-bit application can only load 64-bit codecs, so they are not listed when the application is compiled for x64.

Select instead one of the video compressors available in both x86 and x64:

• the Microsoft and GPU H.264 encoders, included in the VideoCompressors list: “H264 (Auto)”, “H264 GPU (Nvidia)”, “H264 GPU (Intel)”, “H264 CPU (Microsoft)” (the list depends on the GPUs and drivers of the computer); nothing to install,
• the “Datastead Multipurpose Encoder” (H.264, HEVC, AV1…), optional.

The sample code for both can be found here.