If you received an email from Google notifying that some of your ads have been rejected, the first thing you should do is check that this is in fact the case. It may happen that Google performs an automatic revision and then reactivates those ads.
In order to check this, you will have to log into your Google Ads account with the correct gmail account.
Once inside, on the menu to the left, click ads & extensions > ads
On the Ads screen you will have the status column which will mark if the ad was approved or disapproved.
If one of them is disapproved, it will be shown as the following example
When you click on the status, you will see a window with a message indicating why the ad was disapproved. If you consider that the reason indicated is not applicable, you may appeal Google’s decision in "Appeal".
There you can challenge the decision by clicking "submit"
❗️ Please note: we suggest that you read the policy that is not been fulfilled to make sure that it is really worthwhile to ask for revision. If the ad doesn’t fulfill this policy, then Google will disapprove it again.
It is not advisable to appeal unnecessarily, because Google might then restrict the access to this resource.
👉🏼 It is possible that the "Appeal" section is not shown. In this case, if you want to check why the ad was rejected, you have to contact Google’s support center to get an answer. Here’s a form to do it!
The revision might take a few days. Once it is approved, you will see it on the ad’s status with the word "approved".