Did your software vendor indicate that you can virtualize their application, but only if you dedicate one or more CPU cores to it? Not clear on what happens when you assign CPUs to a virtual machine? You are far from alone.
Physical Processors are Never Assigned to Specific Virtual Machines
This is the most important note. Assigning 2 vCPUs to a system does not mean that Hyper-V plucks two cores out of the physical pool and permanently marries them to your virtual machine. I’ve seen IBM systems that do something like this, but I don’t believe that any other hypervisor does. Hyper-V certainly doesn’t. You can’t actually assign a physical core to a VM at all. So, does this mean that vendor request to dedicate a core just can’t be met? Well, not exactly. More on that toward the end.
You can review the whole article at Altaro Hyper-V blog: https://www.altaro.com/hyper-v/hyper-v-virtual-cpus-explained/