@Sarahlm: To troubleshoot this issue please head to Settings > Connections > Wi-Fi > Tap the cog symbol to the right of your router > Forget > Back > Toggle Wi-Fi off and on again > Select your router from the list of available connections, and run through the connection steps. Now, go to Settings > Connections > Wi-Fi > Tap the cog next to your router > Advanced > MAC Address Type, and set this to Phone MAC. If the issue persists, please try pressing the Volume Down and Power buttons together for around 10 seconds until the phone restarts, as this will refresh the software and address any issues that might be a contributing factor. I also recommend resetting your router to ensure that there are no temporary network issues.
If you are still unable to connect then please head to Settings > General Management > Reset > Reset Network Settings. You may also wish to try Settings > Location > Google Location Accuracy > Off, to see if this helps.