This is because the fitness exercise permission in your mobile phone WeChat has not been opened, so there are countless steps in the WeChat movement.
1. Open the settings in the phone.
2. In the settings interface, click Permission and Privacy.
3. In Permission and Privacy, select Permission Management.
4. Next, on the rights management page, click WeChat application.
5. In the WeChat permission, click on the fitness exercise.
6. In the box of WeChat fitness exercise permission, click Allow.
In this way, the authority of your OPPO mobile phone WeChat fitness exercise will be opened, and then you can use WeChat exercise to count the steps.