First terminology. When you say new wiper blade, do you mean just the blade or the wiper assembly? I presume you mean assembly.

Next question. Is this the correct Bosch part, or something else?

Next thought. Does the new part exactly match the old part?

Can you put the old part back on the arm?
You have to insert the hooked end of the arm up through the blade assembly and then pull it until it latches. Hard to verbalize.

Finally, getting the arm to go back down will make you think you are going to break it.
It just requires force.

Steve