What are the possible reason(s) for SRS account application rejected and what can be done?

Hi, I recently tried to apply to open an SRS account with OCBC. Was informed the next day that my application was rejected, with no reason given. Has anyone experienced this before? Any idea what could be the possible reason(s)? I've heard of credit card applications being rejected due to low credit score, but not for SRS account opening. Help!

Heard that it's pretty straightforward to open an account, and didn't think that it would be rejected. I'm tick all the boxes for eligibility (Singaporean, at least 18 years old, not an undischarged bankrupt).