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The arcgissystem folder path warned that the folder was being used be another site. According to step 4 of the documentation, the contents of the initial folder will be copied to the new path. The contents of the azure fileshare folder were emptied and a second attempt was made successfully.
Final check
The initial CSV, hosted feature layer, and web map were deleted and recreated. A CSV containing points (fl_instance_sample.csv) was uploaded as a hosted feature layer, and a web map created. All functions succeeded.