This article explains how to troubleshoot issue when scanning Order unable/failed to open Quick Despatch screen.
Ensure Scanning Mode is ON (Ctrl Shift B)
Check WMS > Tools > Preferences > Barcodes tab.
"Use Special barcode Terminator as (F12)".
Untick this option to allow scanning to be done from RDP session.
Use shortcut "Ctrl + 6" and manually type in Quick