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