Alternative to running VMware Player inside Hyper-V VM, is to install VMware Player on the Windows host itself. Starting with version 15.5.5, VMware Workstation/Player can now coexist with Hyper-V enabled but its hypervisor will be running at ring 3 so it will be slower compared to the normal ring 0 VMM. But probably won't be as bad as running as nested VM inside a Hyper-V VM.
https://blogs.vmware.com/workstation/2020/05/vmware-workstation-now-supports-hyper-v-mode.html
If you still really need to run VMware Player inside a Hyper-V VM,
Did you enable nested virtualisation for the Hyper-V VM?
https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/user-guide/nested-virtualization
Recommend that the CPU is at least Intel Haswell generation or newer for overall better performance in nested virtualisation.
Haswell and newer also has a feature called VMCS Shadowing but I don't know if Hyper-V takes advantage of that in nested virtualisation scenarios.
VMCS Shadowing appears to be available in Intel CPUs with vPro Eligibility indicated as "Yes". So for example, i7-7700K would not have that feature while i7-8700K does.
https://ark.intel.com/content/www/us/en/ark/compare.html?productIds=126684,97129
Assuming if you are able to install VMware Player inside the Hyper-V VM, the vmx configuration file of the VMware VM needs to have the following line added.
vmx.allowNested = "TRUE"
