There are a few reasons why the printer may be printing blank labels:
You may have incompatible stock for the printer e.g. thermal transfer labels in a direct thermal only printer.
There is no ribbon in the printer when using thermal transfer labels.
The software/driver or the printer itself could be running in the wrong mode (i.e. using direct thermal stock, printer is set to thermal transfer mode or vice versa).
The darkness/temperature of the printer is set too low within the software/driver or the printer itself.