The computer won't accept the product key

Most likely, the Acer product key that you see at the bottom of the laptop is for the operating system, and not Microsoft Office. I would first check and see what is written by the code (does it say Microsoft Windows or does it say Microsoft Office Home & Student)?

If you purchased this version of MS Office Home and Student, it should have come with a code. If it came with your computer, Acer should have provided the code somewhere with the documentation.