In normal circumstances a data feed review will take up to 3 working days. However in certain situations this can take longer. There are two elements Google validates, which are your website domain and the data feed.
Google validates your checkout system. If you are collecting personal data than Google requires your checkout to be SSL secured. Meaning that the url must be on HTTPS and not HTTP. In some situations even if you are using a payment gateway that is hosted on a 3rd party website and you are collecting personal data, the chances are that you will need to have a SSL certificate.
A returns policy is required, a link in the footer pointing to your returns policy page is required.
Certain products are in violations with Google’s or the Target Country Law’s. Which means that these products in no circumstances can be listed on Google Shopping.
Here is a list of restricted products.
If the review process is taking longer than 3 days and you have fixed all your data feed errors and checked the above requirements. You can force a re-crawl by appending a query string to your image url’s.
For example if your image is http://www.example.com/myimage.jpg than you can append a query like this http://www.example.com/myimage.jpg?v=06072015
This will force Google to recrawl your data and might resolve your review process. However if this does not resolve your review process than I recommend you get in touch with Google Adwords Team or hire a Google Shopping expert / consultant.