@Henry B ,
From Teams side, make sure you’ve opened the following, for all locations, for media in Teams:
For more network requirements of Teams, please refer to this article.
As our forum does not support 3rd party product, it recommends you contact Synology support for further help. Thanks for your understanding.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.