Check the power to the speaker is turned on, standby red light should flash or solid Green. If not check the connection and try again. 

Go to Settings>Wi-Fi and make sure your network is the same as the speaker when setup if turned off turn Wi-Fi ON. Toggle WiFi on and off, to refresh the connection. 

• Try an iPhone hard reset, press and hold the sleep/wake button and home button at the same time, wait for a few seconds for the device to reboot.
• Try restarting your router this is recommended to be done every couple of months, this can fix internet issues, no internet connectivity to slow wireless connections. This can help the reliability of your home network.
• If you haven't used your speaker for a week, the router could have resigned the ip address to another device, causing connection issues.