So that the Community can help you better, we need to know exactly which Canon scanner model you're using as, to date, Canon USA has not released a scanner with the model number "900F." We have, however, released a scanner called the CanoScan 9900F. Please let us know if that's what you're using or if you've got a different scanner. That, and any other details you'd like to give will help the Community better understand your issue!
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Thanks and have a great day!