cambium ePMP C050900P031A only 20MHz bandwidth?

I have a pair of cambium ePMP model no “C050900P031A”, tried to change the configuration to 40MHz bandwidth but apparently it is greyed out (cannot be selected).

Is this model only support 20MHz?

The model does not restrict 40 MHz channel bandwdith but your country might. What Country are you setting the radio to under Configuration->Radio?