If your UK ETA is refused, it is not recommended to reapply immediately with the same information.
The UK authorities review your passport details, personal information, previous immigration history, criminal records, security factors, and eligibility. If the same information is submitted again, the result may be refused again.
If your UK ETA is refused, you generally cannot appeal the decision. If you still need to travel to the United Kingdom, applying for an appropriate visa may be the correct next step instead of simply reapplying for a UK ETA.
However, if your application was not processed because of an input error, missing information, or a payment issue, you may be able to apply again after checking the notice and correcting the information.
Therefore, if your UK ETA is refused, review the result carefully and consider the proper next step, such as applying for a visa if necessary.