Google disable ad serving on those websites which are not following their policy guidelines. But Google adsense team will usually remind publishers about any issue related to their website before finally disabling the ad serving on respective website.
Google Ad serving disabled on website means that domain is blocked in adsense and until & unless the ban is removed, Google adsense ads will not be shown on that domain. You can add adsense ad codes but they will not show advertisements. That place will be simply shown as blank.
Keep in Mind: Google Adsense Account Disabled and Adsense Ad serving disabled, both are different. In first case, you can not use that adsense account anymore. But in second case, only that particular website will not show adsense ads and if you are having several other websites then as usual they will keep showing adsense ads. In the later one, your adsense account is not block, you can login and use it as you are doing from the beginning.
Actually I faced the same situation this year and got a message in my adsense account from adsense team which is shown below. You will always receive a warning message if any thing is going wrong related to your website content. [ But keep in mind, for fraud click activities, you will never receive any warning mail, your account will be disabled directly and then you will get a mail that your account is disabled for fraud click activities.]
You will get another 72 hours to do specific changes on that website otherwise your adsense ad serving will be disabled on that particular domain name. Since the URL was mentioned in the message so I did respective changes and thought it will be OK. But unfortunately, after 72 hours, I received another mail as shown in the following and was mentioned that the ad serving is now temporarily disabled.
Why Was Wrong in My Website?
Actually the website, disabled for ad serving, was a simple website with a comment box which was not moderated. It means, any one can post any thing in the comment area. After I received the warning, I looked at the mentioned page and found that spammers had done huge spam comment on that page including other pages. Since I deleted the comments from my website but it was still, not moderated. Since the moderation was not yet fixed (It may lead to future spam comments), Google blocked the ad serving after 5 days, instead of 3 day.
What You Should Do After Ad Serving is Disabled?
Once your domain is blocked for ad serving, there is a chance for re enabling your ad serving but you should keep the following points in mind.
1. If your adsense ad serving is disabled due to content issue on your website, you should immediately delete that content page from your website. If the issue is due to comments on your website, you should immediately delete all the comments from your website and activate the comment moderation on your website. If you can not add comment moderation feature, then better to remove the comment feature from your post. Because, if you will not do that then Google may think that this issue may arise in future and hence they may not enable ad serving on your website.
2. If the issue is related to image placement of your website, then you have to change the image placement from each page of your website. If you are just changing the image placement from the reported page and not doing the changes in other pages, then Google will think that the issue may arise in future from other pages so at the end, & they may not enable Google adsense ad serving on your website.
3. If the issue is related to ad placement, then again you have to change the ad placement completely from each pages of your website. Check out this help article regarding ad placement on your website and follow the guideline mentioned there.
Read this Adsense Help to know the type of issue which may arise for your website which may be one of the reason for disabling your Google adsense ad serving.
(If there is another issue, let me know so that I can tell the solution based on your issue.)
What to Do next After Fixing Everything?If you have done everything correct and now you think, your website is not violating the rules again then you can apply for reissue again. Use this form. But I will suggest you to look at the issue and visit each page of your website to know whether everything is going right or not and once you have done everything correct (you have to do this hard work to get ad serving back) & then wait for 1 week before applying for re-enabling. Do not forget to mention what you have done to make sure that your website is now not violating the rules and in future, it will not violate too. Write full details as much as you can in the above form. The more you will describe, the better chance of getting Google adsense ad serving re-enabled.
Best of Luck...