If your wireless network isn’t working the way it should Apple’s “Wireless Diagnostics” can help. It’s at the bottom of the WiFi menu… but only if you hold the Option key before you drop the menu. That is, press and hold the Option key, then click the WiFi menu, then slide down to “Open Wireless Diagnostics.” If you don’t hold the Option key first the Wireless Diagnostics menu item won’t be there.
My friend Tom used to say “It’s always the Option key! I should always try that first!” and he was right. That goes for you too.