I can't confirm for Mercury but for Airwallex, the abovestated is valid. You can try to re-apply.You can try again, Mercury will reconsider the application. Make sure everything is clear, easy to understand, and have contracts + invoices ready to show.
Well, to be honest, the conclusion you have made need not be correct. There could have been something with your application that led to rejection regardless of any improvement, e.g. non-acceptable business type, non-acceptable citizenship or residence of the company owner, etc. Are you really sure that this was not such a case? (Without the detailed information it is impossible to judge.)The second time I reapplied for Mercury they rejected me in 3 minutes. So i think it's automatic afterward.