I used to run DSM 6.1.4 on an HP Microserver Gen8 using loader 1.02b. a few days ago, I accidentally upgrade the DSM to 6.2 beta (it is stupid, i know), and the box just didn't boot anymore.
In Synology Assistant, the Gen8 is not even discoverable (two NICs on Gen8 was configured as Bond connection in 6.1.4).
I tried to prepare a fresh USB with 1.02b Loader, and after the box is booted into reinstall mode, I actually can find the both NIC in Synology Assistant, and the status is showin
You could try the process in this post
Another option could be to use the 'clean drive' install process provided you have a spare HDD and SATA controller port;
1) Disconnect your raid drives
2) Connect spare HDD to SATA port 1
3) Install DSM 6.x, create admin user and server name matching live system, DONT create volume/raid
4) Shutdown, reconnect raid drives to SATA ports 2-n
5) Boot, login, repair system partitions on raid, shutdown
6) Remove spare HD