MacBook shows offline though connected to WiFi

It is likely that your router is not connected to the internet. You can still be connected to your Router and it will show the Wifi icon in your menubar, but the router has no outside connection. Try restarting your router to see if it will establish that connection again.

"Offline" as in, your laptop cannot access the Internet?

If so, then see if the follow Apple Support article can help:

• If your Mac isn't connecting to the internet over Wi-Fi - Apple Support