Why won't my potatoes crisp?
It's almost certanly a variety/potato age thing. 

There are thousands of varieties of potato and different countries grow different ones based on climate and local taste. You can group potatoes in to two sets:


Thicker skinned potatoes that spend longer in the ground as they grow slowly. Varieties sold this way tend to be be a colder weather crop.
The other sort are thin skinned, waxier varieties which include 'new' potatoes. Varieties suited to this grow faster and tend to grow better than the other sort in warmer weather. 


There are 'waxy' firm varieties of the first group but most would be termed 'floury'. These are dryer potatoes and make great mash and chips and roasts and fluffy baked potatoes. 

Waxy potatoes are better for holding together in dishes and salads. These just don't crisp up as well. I assume you're just getting these varieties.