wifi button not working

A greyed out Wi-Fi button often means a defective chip or antenna. Please check this article out. Best to have the phone checked out at an Apple Store.

If Wi-Fi is grayed out or dim on your iPhone, iPad, or iPod touch - Apple Support

Nonetheless, just in case below is a User Tip about Wi-Fi issues. Maybe #1, #2 or #8 will help.

1) Perform a Forced Restart: Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow device to restart.

2) Reset Network Settings: Settings > General > Reset > Reset Network Settings. Rejoin the Network again.

3) Reboot Router/Modem: Unplug from power for 2 minutes and plug again. Update Router Firmware (check manufacturer’s support website for a newer FW). Also try different bands (2.4 GHz and 5 GHz) and different bandwidths (20 MHz recommended for the 2.4 band).

4) Change to Google's DNS: Settings > Wi-Fi > Click on the Network, Delete all numbers under DNS and enter 8.8.8.8 or alternatively 8.8.4.4

5) Disable device prioritization on the router if this feature is available. Also disable any VPN apps and test Wi-Fi again.

6) Determine if other Wi-Fi devices on network are working well (other iOS devices, Macs, PCs).

7) Try device at another Network, i.e., neighbors’, public coffee house, etc.

8) Backup and Restore the Device using iTunes (ask for additional for details if desired).

https://support.apple.com/en-us/HT201252

9) Go to an Apple Store for hardware evaluation.

User Tip: https://discussions.apple.com/docs/DOC-9892

Try a simple Reset: hold down the Home and Power buttons until you see the Apple logo (10-20 seconds).

If this doesn't help, you might need to Restore your iPhone.

https://support.apple.com/en-us/HT204184

Sorry for asking such basic questions, but I'm not clear on what's going on...

In Settings > Wi-Fi > Wi-Fi is ON (green), right?

And you selected your network from the Coose A Netwirk list?

You entered your network password (if asked), but the network did not receive a check mark as being selected? Or it is selected but the icon there is grey?

Please check this close to your Wi-Fi router.

In Settings > Wi-Fi > is your network shown as connected?

Check if Airplane Mode was switched on accidentally.