I have not used it for this year, (was switched to a APAP in Jan. 2016) but for new medical reasons dug it out and started using it yesterday morning (7/20/16).
First night was from 3:30AM to around 6:00AM yet is only shows about 35 minutes.
Next is last night I went to sleep around 9:00PM and woke up at around 12:00AM and it only showed around 35minutes.
I rebooted it, and switched SC cards. Then slept another three hours and again it does not show the elapses time.
It does show the correct time and date, but not the total sleep time…
What can I do to fix this??