Why did technology make it difficult for armies on the western front to mount successful offensive attack?

Answer: Because enemies were able to detect and suppress the weapons.

Explanation:

Because the technology did allow improved and new weapons that allowed a new way of fighting.

Enemies were able to detect weapons and find out what are those weapons, are they filled with something and other so they were having the possibility to suppress them,

For example, Germany had enemies that detect their weapons. They found how to suppress those weapons (it was the zeppelins filled with hydrogen) and avoid them.