Please do not offer to pay here. Users of this forum are willing to help if they can and you do not need to offer payment for a solution to your problem. It won't help.
Topic specific answer: the interesting thing is that the bios seems to recognize all the GPU(s), which is already good. Indeed, it seems somehow related to the driver.
Could you give output of:
lspci | grep VGA
too
did you try to use another operating system, like windows, with the same 5 GPU system? Maybe that could help to identify the problem...
I'm sure some other people (like epixoip) have more ideas....
and yes, in general we tell people to avoid risers wherever possible, since they lead to very strange problems (but not sure if that is also the case here).
P.S. also some system log files (also dmesg) could help to troubleshoot this problem
Topic specific answer: the interesting thing is that the bios seems to recognize all the GPU(s), which is already good. Indeed, it seems somehow related to the driver.
Could you give output of:
lspci | grep VGA
too
did you try to use another operating system, like windows, with the same 5 GPU system? Maybe that could help to identify the problem...
I'm sure some other people (like epixoip) have more ideas....
and yes, in general we tell people to avoid risers wherever possible, since they lead to very strange problems (but not sure if that is also the case here).
P.S. also some system log files (also dmesg) could help to troubleshoot this problem