I am only sometimes getting the Turnitin Pencil icon for assignment submissions, as shown here:
You can see it is missing on the first assignment, but appears on the second.
Does anyone know what is going on?
The submission without the grademark link may not have submitted to Turnitin. Which version of the plugin are you using? More recent versions contain a Paper Id above the grademark link and would show an icon to indicate an error if one has occurred in the submission process.