there may be a function (e.g. shift+F3) or switch to turn the wifi OFF on your notebook, that you may inadvertently have activated.
Suggest you check carefully the User Manual, and if so, turn the wifi back ON.
Another thought, perform a cold boot on the router by disconnecting from the mains supply, wait a few seconds, then power it on.
Please advise back on progress.
Good Luck - Keep us posted.