The 1026TT-TF is based on an SC809 chassis (PDF manual). Checkout Appendix C for information on the backplane, you'll have the "TQ" version with SAS support and the chassis management chip, not the "T" version*.
Check all of the cables running in to the backplane in each compute node and compare them with the diagram on page C-3. You should have a 4-pin power connector plugged in to the top, and four SATA/SAS cables connected. The 10-pin header next to the 4-pin power connector is connected to your RAID card or to the motherboard, that'll be the sideband cable that the FAQ speaks of.
You may also try a reset of the controller chip as documented on page C-6, though I have no idea if it could be contributing to the problem.
*: This manual is only for the "T" chassis. The letters after the numbers but before the dash indicate the type of drives the chassis takes. "TQ" means SAS/SATA hot-swap, while "T"s usually don't have SAS support. We're lucky enough to have the "T" manual cover both the "T" and "TQ" backplanes.