I made some changes to my origin server which now serves different data from same url.
I tried to clear my cache completely by doing the following invalidation in CF
You need to use /* instead of /.
/*
/
Also, if you need to do this frequently, you can do it using the AWS CLI.
aws cloudfront create-invalidation --distribution-id=YOUR_DISTRIBUTION_ID --paths "/*"
Edit: thanks to @speckledcarp, you need to use "/*" (with quotes) when using the CLI.
"/*"