Every advert posted on Google has got to conform to google policies. If your advert is continually being disapproved it means that there is a policy infringement. The good news is that Google always provides you with the reason for disapproving your advert. So here is how you can resolve your issue.
Check to see what policy the advert has violated.
Read the policy carefully taking notes on what you are doing wrong:
Fix the error and save your advert.
Google will review your advert, if there are no violations your advert will run
It is important to note though that there are some products and services that are not eligible to run on the Google Ads network. If you are running campaigns specifically for such services, unfortunately, the ads won’t be approved.
I hope that helped if you are still having problems contact Google directly to ask for assistance