Pre-approved and then rejected and no explanation provide

I app**** for a loan to consolidate my debt in mid December 2019. I was pre approved for a good amount at an installment of +/-R1700. I also explained to the agent that the installments they were picking up on their system were incorrect as this also caused a decline in a previous application. She understood and made a note. She was a pleasure to deal with. A few days later I called in to follow up and was told that the application was declined due to affordability. Clearly no one felt the need to let me know. I had to follow up to get feedback. I couldn't understand how that could be so I emailed to for an explanation. To this day I gave not gotten an explanation from the department that declined my application.