We have 870 32C ... I know on ours you must set how the port is partitioned if you are using anything other than 100 gigs... If you did not do this then a 40 gig link will not come up.
configure ports 45 partition 4x10G
configure ports 49 partition 1x40G
Any partition changes will not take effect until you reboot the switch so think through on how you want to lay our and use the ports as best as you can before you put this into production.
I also see a CFP converter in your diagram. Those can be tricky to get up at 100 gigs due to differences in how some vendors do FEC...
https://documentation.extremenetworks.com/exos_commands_22.3/exos_21_1/exos_commands_all/r_configure-ports-partition.shtml
https://community.extremenetworks.com/data-center-slx-vdx-mlx-ces-232983/can-t-get-a-link-between-a-870-qsfp28-sr4-100-gig-and-a-brocade-mlxe-100-gig-using-cfp2-to-qsfp28-module-7735357