Issue expanding RAID 5

[alisaman]

I am using AS6404T with 3 8TB WD RED drives with 1.4 TB free space. It is mostly PLEX movies and few GB pictures. 4 days ago I added 4th 8TB RED drive to the RAID 5 and configured expanding the raid to 4 drives. Shortly after that, I lost connection to the NAS via browser/Control center (status Not ready). It is still online, and turned on. I can use the physical buttons on the NAS and it is still on the local network. I tried to force restart via physical interface about 30 hours ago - the NAS screen is since then showing "Restart please wait" status - so it could look like NAS is working on expanding the raid, but I do not hear the discs working. Any ideas whether it just takes this long to expand raid5 with 8TB drives? And why am I not able to access the NAS?

[orion]

Shortly after that, I lost connection to the NAS via browser/Control center (status Not ready). It is still online, and turned on.

What do you mean about "still online, and turned on."? What tool do you use to check online status? (You said that you cannot connect to NAS via browser and control center.)

You should be able to check NAS status via browser when expanding RAID-5 volume. You can see the percentage of expanding process. You can even access your data when expanding although the data rate should be lower. The LCD screen information is too rough. If you cannot still connect to NAS via brower, you should send a support request to asustor directly. https://support.asustor.com/

[alisaman]

The nas in still on the local network, but the GUI interface is not accessible via browser/asustor app. I lost this connection shortly after initiating merging the 4th disc via GUI interface

[orion]

How do you make sure that "the nas in still on the local network"?
Anyway, it's definitely abnormal that browser lost connection. You should contact to asustor support.