Your code don't use your created texture. It creates a texture:

// Create temp frame buffer(2d texture)
wrl::ComPtr<ID3D11Texture2D>pFrame = nullptr;
HRESULT hr = pDevice->CreateTexture2D(&pFrameDesc, nullptr, &pFrame);
GFX_THROW_INFO(hr);

Then it loses track of that texture and takes the one from the swapchain (which is never set for CPU READ):

hr = pSwapChain->GetBuffer(0, __uuidof(pFrame), &pFrame);
GFX_THROW_INFO(hr);

Then you try to map the swapchain buffer:

hr = pContext->Map(pFrame.Get(), 0u, D3D11_MAP_READ, 0u, &map);
GFX_THROW_INFO(hr);

Your code doesn't use your created texture with D3D11_CPU_ACCESS_READ. 

It creates a texture:

// Create temp frame buffer(2d texture)
wrl::ComPtr<ID3D11Texture2D>pFrame = nullptr;
HRESULT hr = pDevice->CreateTexture2D(&pFrameDesc, nullptr, &pFrame);
GFX_THROW_INFO(hr);

Then it releases that texture and takes a reference to one from the swapchain (which is never set for CPU READ):

hr = pSwapChain->GetBuffer(0, __uuidof(pFrame), &pFrame);
GFX_THROW_INFO(hr);

Then you try to map the swapchain buffer:

hr = pContext->Map(pFrame.Get(), 0u, D3D11_MAP_READ, 0u, &map);
GFX_THROW_INFO(hr);