Hello Preecha Sungum,
Thank you for posting in Microsoft Community forum.
I'm sorry to hear that you're having trouble activating the CalDav license for Remote Desktop Service on Windows Server 2019. Here are some steps you can try to resolve the issue:
- Check that you have entered the license key correctly. Make sure there are no typos or extra spaces.
- Verify that the license key is valid and has not expired. You can do this by contacting the vendor or reseller who provided you with the license key.
- Ensure that your server has an active internet connection. The activation process requires an internet connection to communicate with Microsoft's activation servers.
- Try activating the license again after restarting the Remote Desktop Service.
If possible, please provide a screenshot of the current issue.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Haijian Shan