It takes many previews to just get a glimpse of my ad. I do not know. Why does adwords sometimes show and when previewed again it does not show. Any Idea?
This is because they are limiting the amount of times your ad is displayed based on the amount of budget you have set for your day, versus how much your competitors have opted to spend for the day.
You can change your ad delivery method to
accelerated delivery but that would mean you would spend your budget far quicker and your ads will not display for the rest of the day.
See this page for more information.
Your ad in Google Adwords depends on many factors like your budget, ad rank, quality and how your competitors are competing with the same. You need to test it out by appylying variations to your ad group. Create similiar ad with different variations with different budget, write new ads in different format and try to increase your ad rank.
Often times your ad may show intermittently if you have just set up your ad group or campaign. Make sure that you have 1. Competitive bids, 2. High quality score for the keywords that you are using to trigger the preview, and 3. Be sure that your IP address is within the geographic area which you are targeting. For example, if you are using a VPN from another country, and you are targeting the USA, you won't see your ads.
Lastly, a quick fix to this problem would be to change your campaign settings for ad delivery, and chose accelerated. The default/Standard will show your ads slowly throughout the day.
Another trick you can try is to view the keywords within your adgroup, and hover over the bubble. Doing this will tell you immediately whether or not your ad is showing, without having to use the ad preview tool.