Internet connection doesn’t work anymore

My computer is in the repair shop and won't be fixed until next week. So I bought a new desktop computer so that I can finish my online job and projects. I am currently working on an article and I need a lot of web researching. So I plugged my computer to my modem and turned it on. But it doesn't show any internet access, unlike my other computer. The computer I bought is exactly the same one in the repair shop. What should I do?
