It seems that multiple issues with your drive occured rendering the volume dead. I would recommend contacting support for recovery. Note that they may ask for a Data Recovery contract.
Alternatively, you can use 3rd party recovery software as recommended by other community members. r-studio, reclaime etc.
Either you removed two drives with the system still on, or the system "removed" them from the volume because of a problem with them. Removal of two drives from a system without sufficient time for a re-sync in between will render the volume dead. Unfortunately, some mistakenly believe they can simply re-insert a drive if "nothing has changed" and not need a re-sync. But the removal itself is a change when power is on.
Unfortunately, those re-sync completions you see in the log are not your data volume, they are the OS volume. They are not long enough to be the data volume, and I have seen this behavior before. Netgear REALLY needs to correct that issue, as it has led others to remove a drive while the data volume is still in re-sync with another drive, rendering the volume dead. But that doesn't seem to be what happened here, though.
