Because you didn't click on the original picture to send. Click on the original image below while clicking on the video, and you can send high-definition video. Let me share the operation steps:

The software version is 8.0.28. Mobile phone model: vivo Y31s.

The operation process is as follows:

1. Open the WeChat software on your mobile phone and click on the chat interface you want to send to enter.

2. Then click the+sign in the lower right corner.

3. Then click on the album.

4. After entering, select the video, and then click the original image.

5. Just send it last.

You can also click the file through the plus sign, check the file to be sent, and finally click Send to the other party.