Please try to run WSUS server cleanup wizard.
According to the screenshot, the first sync is successful, but there is no update. So please check the network is normal, is it synced from Microsoft directly? If not, please change it and see if it succeed.
Besides, please check SoftwareDistribution.log for further information, it provides information about the software updates that are synchronized from the configured update source to the WSUS server database.
If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
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.