Invalid flavorRef Supplied HTTP 400 Error in OpenStack

Hello guys! I have used OpenStack by XenServer. I found the following error message:
(No flavor with a name or ID of ' ' exists) when I want to run "nova boot test12_88 –flavor 2 –image 9e554483-bec0-4e13-80ad-648004dd7425 –key nova_key" and if I restore the flavor ID and flavor name (m1.small), ERROR is "Invalid flavorRef supplied (HTTP 400)".
Does anyone here have any thoughts about this?
