Hello,
Since the release of Sequoia 15.0 is quite recent, no compatibility issues between the RD client and specific server versions have been reported on this forum yet.
Have you verified the network connectivity between your macOS system and the host server?
Have you made any recent configurations or updates on the problematic server side? Additionally, attempting to restart the problematic server might resolve any potential glitches.
Try connecting using a different RDP client: Get started with Windows App to connect to devices and apps - Windows App | Microsoft Learn or test with the Bata version App Center.
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