This tooth was referred to my office today after the RCT had been started. I appreciate a dentist who is not afraid to stop during a procedure and refer if needed. Here's a tip to help you find these canals.
Look lingually. The natural access into a Md incisor always goes toward the buccal. If you cannot find the canal (or the second canal in 20-40% of these teeth), look lingually.
I used an ultrasonic tip under the microscope to cut from the current access back towards the lingual.