This issue often happens when the binary you're trying to run requires AVX support, which not all CPUs, especially older ones, offer. You might have an older CPU without AVX support, which is necessary for the encoding used by Walrus. If you are running in a virtualized environment, this might also be caused by a misconfigured VM. A possible fix is to install the ubuntu-x86_64-generic version of the binary instead. This version is specifically compiled to ensure compatibility with nearly all physical and virtual x86-64 CPUs. You can download it from the Walrus documentation resources. Make sure you are also using the correct versions and configurations as specified by the Walrus documentation, which could help avoid compatibility issues.