The remote desktop may not be able to copy and paste for the following reasons:
1. Run > mstsc > Display Options > Local Resources TAB > Local Devices and Resources > Details... > tick "Drives"
2. An in-progress copy-paste operation was abnormally interrupted . Check whether the rdpclip.exe process is enabled: open the server task manager -> view process -> look for rdpclip.exe, if it exists, you can end the process and re-run it; you can use win+r to call up the run box, enter rdpclip and press Enter.