Clear the cache
I had the same problem. I am using Android so if you're using the same try these. Some of the online solutions (that did not work for me) were:
Switch off mock locations ( it was already switched off)
Turn on location to high accuracy ( already done)
Update Google maps ( did it, yet couldn't fix problem)
Reinstall app ( 3 times)
Switch off mock locations ( it was already switched off)
Turn on location to high accuracy ( already done)
Update Google maps ( did it, yet couldn't fix problem)
Reinstall app ( 3 times)
None of the solutions given online worked.And then I thought for myself. So
So what worked for me? I went to downloaded apps, selected Pokémon Go and cleared cache and data.
Caught Charmander :)