From what i understand, you are splitting the ports on Arista Switch 4x10G and one of the split cable is connecting to FSW.
Whats the speed config on Cisco and FSW? Please try to have same speed config on both sides, may be set to 10000auto or 10000full.
Is the FSW on latest version 7.0.4 ot 6.4.10?
get switch modules summary - is the module in any error or alarm state?
We can check the switch log after you connect the module to the switch.
execute log filter view-lines 1000
execute log display
diag switch physical-port summary port#
Wifi-Switching – International Support