Do you have enough available power in the system for 2nd supervisor?
Such errors message are reported is there is some type of mismatch between two supervisor modules.
It is a generic error called when the amount of power drawn by the standby supervisor is not the same as the active one, causing the standby not to boot properly; this in turn causes the standby not to reply from active supervisor's polling, causing redundancy to fail.
Causes of this issue are the following:
- Mismatching HW, e.g. different DRAM amount
- Faulty supervisor (or Supervisor with different ROMMON/hardware version)
- Faulty chassis
- Seating problem
Check if the they have matching memory amount and reseat the chips (especially on MSFC as you mention it is not detected). If DRAM is fine but the issue is still seen, you are likely to have HW failure (dead MSFC for example) and need to replace the problem supervisor.