The reasons for restricting IOUs trading are: IOUs have been used, IOUs are overdue, transactions and personal information are abnormal, personal qualifications have changed, and the system misjudges. The solution is as follows:

1. White bills used: White bills can be recycled. After the user purchases goods with IOUs, this used bill will be temporarily frozen until the IOUs repayment form is issued and the user pays off the debt of using IOUs. When users find that the use of white bars is restricted, it is probably because the previously used white bars have not been returned, which leads to the inability to continue using them.

2. Overdue due to the use of IOUs: IOUs are loan products that give credit according to the credit rating of users. Once the user's credit rating changes, the IOUs system will restrict users from trading with IOUs. If the user fails to pay the arrears when using the IOU, the system will downgrade the user's credit rating, resulting in the user not being able to use the IOU normally.

3. There are abnormal transactions and personal information: if the system detects that users use white bars to cash out, lend them to others or use them in other non-compliant payment scenarios, then in order to avoid risks, the white bar system will restrict users from using white bars. Similarly, if the system detects that the personal information of the current user is inconsistent with the personal information when the user applied for opening the white strip, it will also restrict the user from using the white strip.

4. Personal qualifications have changed: in the process of using IOUs, users' assets and liabilities have changed greatly, or users' current income level cannot bear the responsibility of repaying IOUs bills on schedule, or even if users are in a state of restriction or lack of civil capacity and are included in the list of untrustworthy people, when IOUs system detects these changes, it is likely to reduce the amount of IOUs used or restrict users from using IOUs for consumption.

5. System misjudgment: If the above factors are excluded, or the IOUs transaction is restricted, it is likely that the system misjudges when monitoring the account risk, resulting in the user's IOUs account being locked.

6. If the account is locked due to system misjudgment, the user can complain to the customer service and provide evidence to prove that his account transaction is safe and there is no credit problem. After verification, the customer service will unfreeze the white account for the user.