No backup file found after scheduled backup from sleep mode. No display after wake.
EDIT: I have just found what was going wrong with what is described below and now the problem appears to be solved. I'm posting here in case anyone else who has the same issue finds it useful. If anyone else has seen a similar issue and can help with a better understanding - please post here. Thank you.
About 10 days ago, I installed Aomei Backupper pro on a new AMD Ryzen System with a clean install of windows 10 pro. Initially I installed version 5.5. However scheduled backups were not taking place in 5.5 (from sleep mode). In fact the system appeared to be crashing in the middle of the night when the backup was scheduled - I won't go into the details, event viewer entries etc. Also there were no entries for Aomei in the Windows Task Scheduler.
I thought the problem may have to to with backupper not handling the sleep mode properly. Therefore I installed version 5.6 after uninstalling 5.5. In version 5.6 there is an option in the Aomei GUI for waking the system from sleep which I have checked. Now, after installing 5.6, the windows Task Scheduler correctly shows all the scheduled Aomei entries. Also, the scheduled backup works fine in the wake state. However, not so in sleep mode.
To isolate the problem, I did the following test several times. I set display to turn off after 1 min and sleep after 2 mins and scheduled a small backup to take place a few minutes after sleep. I then watch the fan activity on the machine - sure enough at exactly the scheduled time the system wakes up, the display shows and the fan speeds up indicating that some processing is taking place and then the fan speed returns to normal. Around this time the display also goes blank again (since it has been set to go off after 1 min). I then wait a couple of minutes and then shake the mouse - and there is no response from display. The only option is to do a hard reset.
Looking through the Event Viewer (Windows Logs/Application) I found the following entry (Event Id 8194, Task Category: None):
Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface. hr = 0x80070005, Access is denied. This is often caused by incorrect security settings in either the writer or requestor process.
I couldn't understand why there should be such an error. However it suddenly occurred to me that while my windows system was installed on a brand new drive, my data drives, including the backup drive, had been transferred physically as-is into the new machine. So on the backup drive, the security user/group names showed: Authenticated users, System, Administrators, Users and Unknown User - the unknown user being from the installation on the old machine. Still, I felt that that could not be the problem as I (current user: Sandeep) had administrative rights (I usually remove admin rights after everything appears to be set up and functioning smoothly). Nevertheless on the off-chance, I added "Sandeep" to the list in the security properties box in the backup drive, but giving only read-execute rights since I would be doing that anyway later. Then I repeated the sleep + scheduled backup test as above and lo and behold everything went as smooth as butter.
The blank screen in the original test was probably hiding a BSOD underneath - which could not be seen as the display had been set to timeout in one minute. In fact doing the same test but shaking the mouse before the one-minute display timeout brought the windows 10 blue screen - We are checking the problem etc, etc, and going from 0 to 100%.
So although I cant quite understand what the "Access denied" problem was, adding the correct user (even with limited rights) seems to have resolved the problem. I will have to see how it goes over the next few days. If anyone else has seen a similar issue and can help with a better understanding - please post here. Thank you.