Look in Device Manager - is a bluetooth device listed. It is probably a Broadcom device. If it shows a triangle warning, it is likely that you need to find the appropriate bluetooth driver.
PGC-71911M is a generic model code for a series of vaio models with different specifications. See if you can find the model code used by Sony Support - this will start VPCE*********
Sony no longer supports driver downloads for Vaios released with Windows 7 but if you can find the model name, it should be possible to find the correct driver.
The model name used by Sony Support will be something like VPCEH1S0E. It will have a support website here:
https://www.sony.co.uk/electronics/support/results?query=VPCEH1S0E
You can see that this particular model uses a Qualcomm driver and shows the importance of finding the correct VPC***** model name.
