1. Complain to the APP platform: you can reflect the problem through the customer service or complaint channel of the APP platform, and provide relevant evidence and materials. If there are illegal acts or improper operations on the APP platform, you can report to the relevant departments and ask for investigation.

2. Apply for a refund from the bank: If you paid a certain fee when using the APP, and these fees were paid by bank card, you can apply for a refund from the bank. Need to keep relevant payment records and vouchers, contact the bank customer service for processing.

3. Seek legal aid: If the loss is large, you can seek professional legal aid. You can consult a lawyer or legal service agency to find out whether there is a common way to recover losses through legal means.