Unfortunately, the lock cylinder can be a common failure point on older V70s.
First, make sure of the battery and fuses etc. When sure of all supply voltages, pull the bottom column cover and remove ignition switch on left side
from the lock cylinder assembly. Then you can turn the center part clockwise with a screw driver just as the key turns it through the lock cylinder. If it
now works, it is the lock cylinder. It could also be the ignition switch itself if you cannot get the normal idents for power to the accessories and then
the starter.