Hello,
The cause for this problem is scan function may occasionally default to use PC Local (USB).
See if this solution helps you:
On the printer operational panel > select scan (notice at the top "PC Local (USB)") > select Save/Forward on the bottom left > use up/down buttons to scroll through the short list of PC targets to select one of the named PCs > press the OK button (notice at the top the named PC is now showing.
Hope this helps!
Reference: https://community.usa.canon.com/t5/Printer-Multifunction-Support/Set-the-PC-to-Start-scanning/td-p/42271.
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