Hello,
Check group policy in your server:
Launch "gpedit.msc".
Navigate to "Computer Configuration" > "Administrative Templates" > "Windows Components" > "Remote Desktop Services" > "Remote Desktop Session Host".
Ensure "Do not allow Clipboard redirection" is set to "Not Configured" or "Disabled".
Note: clipboard only allow files smaller than 1 GB. You should check your software if you are not using "mstsc", and confirm the advanced options.
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