No one can guarantee that trademark registration will be 100% successful. There are objective reasons and subjective reasons. If the trademark registration is unsuccessful, the Trademark Office will not refund the money. If your trademark application is rejected by the Trademark Office, you can consider a review. If the review is successful, you can also get a trademark certificate. If you cannot obtain a trademark certificate in the end, it means that the trademark is invalid and any further use of it will not be protected.