How long does it take for the data to appear in Google Analytics?
Google analytics takes up to 24 hours for the data to appear. GA will show reports from the day you have implemented tracking id on your website. It will not show any historic data or the number of visitors who visited the day before you implemented GA.
In some cases it happens that you implemented google analytics tracking id and waiting for days to appear data and wondering what could have happened. The best thing to do is to check the tracking id when you first setup GA.
There are multiple ways for checking if you have inserted the tracking code correctly. One simple way to check is by installing Google Tag Assistant extension for chrome. It will show the tracking id and the status if working or not.