I have a QNAP TS-873-8G that when turned on only the LAN led is blinking orange.
Powerled and statusled stay off. This is with only one stick of memory and the disks and m.2 cache taken out. If I put it in like I have used it before only the LED of disk 1 and disk 2 are on. This while all slots are taken. Is there anything I can do to get it back up and running? Is there a possibility for a firmware recovery?
Does the NAS boot into setup without any disks installed?
If not, you need to contact support, as your unit does not suppport firmware recovery
https://www.qnap.com/en/how-to/faq/article/nas-recovery-guide
Thank you for your answer. No it does not boot up without disks.
I will contact support to see if they can help
“Into setup” meaning you will have to find it via DHCP server or Qfinder..just to make that clear
I understood 
It does not get an IP anymore and Qfinder does not find it either.