It is possible that your internet connection or the other user's connection is preventing content sharing during a call. You can check your internet connection by using another app that uses an internent connection like a social media app.
- If the connection seems slow, it could take some time to fully load the content being shared.
- If other apps do not work normally, try switching to a different network or using cellular data instead of wifi, then ask the other user to try sharing the content again.
If the internet connection is fine, you could be trying to share an unsupported file type. You can check this list to make sure the file you are trying to share is supported by FYI.