Here is a way to check is virtualization is enabled or disabled by the firmware as suggested by this link in parallels.com.
How to check that Intel VT-x is supported in CPU:
Open Terminal application from Application/Utilities
Copy/paste command bellow
sysctl -a | grep machdep.cpu.features
Mac:~ user$ sysctl -a | grep machdep.cpu.features
kern.exec: unknown type returned
machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM SSE3 MON VMX EST TM2 TPR PDCM
If you see VMX entry then CPU supports Intel VT-x feature, but it still may be disabled.
Refer to this link on Apple.com to enable hardware support for virtualization: