Dell PowerEdge FS12-NV7 not booting to POST. Amber lights flashing

I wonder if somebody could help me. I have purchased a server rack which contains 6 FS12-NV7 servers. However, when powering them on, only one boots to POST. The other 5s warning amber light flashes 3 times repeatedly; two flashes followed by a quick double third flash. I would hugely appreciate it if somebody could assist me with this. As all 5 are doing this, there is clearly a common denominator. I have reset CMOS on one of them, assuming the jumper next to the battery is the CMOS reset (cannot find any documentation whatsoever, apparently it is a unique specifimen). No change. I haven’t hooked it up to the network yet, I wouldn’t have thought that was necessary in order to get the system to POST.

I am to believe the system is similar to more common servers such as FS12-TY, which is essentially the Intel version, which itself is basically a C2100.

Apologies if I have posted this in the wrong place.

Thanks in advance for any advice.