Hey Folks,
I'm not 100% sure if you're trying to have 2 Domains, 1 with 62xx FIs, 1 with 64xx FIs or if you're trying to replace the 62xx with 64xx. So hopefully something below will help you.
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/ucs-manager/GUI-User-Guides/Firmware-Mgmt/4-1/b_UCSM_GUI_Firmware_Management_Guide_4-1.pdf
Looking at the error message, it looks like you're trying to downgrade the UCSM, the FIs, and the Chassis IOMs.
This suggests, there is an enabled Feature in the 4.1x Firmware, which is not supported at the 4.0(4d) level.
See Checklist Item# 6.
And the then highlighted towards the bottom, "... .bin is not available or valid for this setup"
Unsupported Features Must Be Unconfigured Before Downgrade
If you plan to downgrade a Cisco UCS domain to an earlier release, you must first unconfigure all features from the current release that are not supported in the earlier release and correct all failed configurations.
Curious, why you would want to downgrade at all. UCS is generally backward compatible.
You could update the Infra of the 62xx FI to 4.1, which would support Firmware on the Servers/Blades all the way down to 4.0(1).
If you're replacing 62xx FIs, with 64xx FIs see this section:
Firmware Upgrade While Migrating from Cisco UCS 6200 Series Fabric Interconnects to Cisco UCS 6400 Series Fabric Interconnects
"These upgrade guidelines must be followed while migrating:
• The Cisco UCS 6200 Series fabric interconnect should be upgraded to Cisco UCS Manager Release 4.1(1) or later releases.
• The Cisco UCS 6400 Series Fabric Interconnect must be loaded with the same build version that is on
the Cisco UCS 6200 Series Fabric Interconnect that it will replace."
Something to look out for:
Be cautious of low Firmware on Blade/Server VIC Cards, as some might require an upgrade, if going to 4.1.
Table 14. Minimum Software Versions for Adapters
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/release/notes/CiscoUCSManager-RN-4-0.html#concept_rlp_4h2_zdb
If all else fails and you don't mind rebuilding the 64xx FIs, you could erase the configs and start from scratch by only upgrading the FI's (UCSM, System/Kernel). I'm not 100% sure what would be needed at the Chassis/IOM level, so please verify.
https://community.cisco.com/t5/unified-computing-system/ucs-fi-6248up-fabric-interconnect-lead-state-inapplicable-mgmt/m-p/3322086#M24702
The better option in my opinion, would be to upgrade each FI 62xx, (Subordinate Upgrade, Failover, then Upgrade the new Subordinate), to 4.1, in a Maintenance Window.
Good Luck
