Check if one or more of your blades have a fiber channel card (or other non-ethernet card) in their B-mezzanine slot. If so, this would cause this message. You can easily see this in the M1000e web ui.
Have 1 M1000e chassis with A1-A2 containing M6220 IOMs. Slot C1-C2 have M8024 switches. This is working. I installed a second set of M8024 in B1-B2, and they will not power up due to IOM Fabric Mismatch. Is there a limit to the number of M8024 switches I can install in the chassis?  K
M1000e Chassis and M8024 Switch quantity?