You should be configuring it as per the following guide
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/interfaces/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide/b_Cisco_Nexus_9000_Series_NX-OS_Interfaces_Configuration_Guide_chapter_0111.html#concept_084B6860BD4C467D8B89DFACE07ECE05
You can enter the show vpc brief and show vpc consistency-parameters commands and check the syslog messages.
You configure the port channels by using one of the following:
>> No protocol
>> Link Aggregation Control Protocol (LACP)
When you configure the port channels in a vPC—including the vPC peer link channel—without using LACP, each device can have up to eight active links in a single port channel. When you configure the port channels in a vPC—including the vPC peer link channels—using LACP, each device can have eight active links and eight standby links in a single port channel. (See the “vPC Interactions with Other Features” section for more information on using LACP and vPCs.)
Manish