Dell emc s4148T-ON & Dell Force 10 MXL switch connectivity issue

Dear Communities

We recently purchased Dell EMC S4148T-ON and Dell force 10 MXL fabric switch. Both switch support 10 and 40 Gb port. When we tried to connect S4148T-ON to force 10 MXL switch using 40 Gb QSFP cable the port shows as down. We tired to connect 40 Gb port.

We checked the cable . Its working. When we loop switch particular switch port using QSFP cable the port shows up. We tried this on both switch.