Grindr uses GPS technology in your device to determine your location. Follow the steps below if Grindr's got you in the wrong spot, or if Grindr's not finding people in your area.
First, force close Grindr:
Apple iOS 8 + Users:
From the Home screen, double-click the Home button to view the multitasking screen.
Locate the Grindr window.
Swipe your finger from the bottom to the top of the screen over the Grindr window.
Restart your device.
Open Grindr.
Then, check your current location:
Open Maps 
on your device.
Tap Current Location at the bottom left.
Now, reset your location services.
Open Settings 
on your device.
Tap Privacy, then Location Services.
Toggle Location Services to off. Tap Turn Off.
Restart your device
Open Settings on your device.
Tap Privacy, then Location Services.
Toggle Location Services to on.
Scroll to Grindr and set Location Services for Grindr to While Using.
Open Grindr.
Be sure to also check your data connection. When you're using a Wi-Fi network, location is determined by the network's IP address. Disable the Wi-Fi settings on your device and try using Grindr with only a mobile (3G, EDGE) network connection.