My Wi-Fi won't connect on my laptop but will connect to my other devices (an iPhone and iPad)?

I have a MacBook Air. Sometimes it does connect but other times it just won't. It takes ages connecting and then in the end comes up with the exclamation mark or is just blank. Is this a problem with my laptop? I've tried researching the problem but have found nothing.

It is possibly an incompatibility between the laptop and your router. From my own experiences this affects between 2% and 5% of pairings between specific routers and devices.

Try connecting to a friends Wi-Fi network (obviously with their permission). If this works properly, then adding a wireless access point to your network, possibly installing a different wireless driver in the Mac or using a USB wireless adapter (with its own drivers) might solve the problem.