Laptop won’t connect to extender but other devices can

Would need more information to answer this. You'll need to know what WiFi adapter is in your laptop. What can it connect to?

Example: If the laptop only supports type A/B/G and your extender is using N - That would do it.

Check your settings on the router and make sure the extender is set to use the same network type as the router.

Try this

Check out the advaced settings for "802.11a/b/g Wireless Mode or Wireless Mode". That's where you can tailor your connection to a specific technology. Be warned, that could mess up your connections to other wifi providers.

I've found that Dell laptops tend to have this problem frequently. I recommend updating the driver for the network adapter (go to Device Manager - Network Adaptor - right click on network adapter and pick update driver).

Also, update the BIOS on your laptop. The easiest way to do that on a Dell is to use the Dell SupportAssist tool and choose to update BIOS. Other brands have similar tools.

One of these two usually fix it without having to mess with the adapter settings.