1. Incompatible video format: Some competitions may require specific video formats. If the video format is not compatible with it, it cannot be uploaded. You can try to convert the video into the format required by the competition and upload it.

2. The video size exceeds the limit: some competitions have restrictions on the uploaded video size. If the video size exceeds the limit, it cannot be uploaded. You can try to compress the video size before uploading.

3. Network problem: uploading video requires network support, and unstable network or slow network speed may lead to upload failure. You can try to change the network environment or wait for the network condition to improve before uploading again.

4. System problems: There are system problems in the competition platform, which may also lead to upload failure. You can try to contact the organizer for technical support, or wait for the system problem to be solved before uploading again.