Can't stick Bale spike into hay bales?

Early on in the game I ended up purchasing a bailer and didn't realise I'd need some tool to move the hay bales. I bought a front loader with a bale spike and I was able to stick it into the hay bales and sell them. 

I have recently created loads of hay bales but for some reason I am unable to stick the bale spike into the hay bales. What has gone wrong?

This is a common enough bug with the game. If you save, quit and reload the game you will usually find that the issue has gone away.