In Openstack (devstack) i am able to create maximum of 3 volumes only

I have 3 volumes of 80GB each and when i try to create a volume snapshot or a new volume i am not able to do that. i get the error 'schedule allocate volume:Could not find any available weighted backend'. The volume quotas are set properly yet i am not able to create more than 3 volumes. i have attached screenshots of the volume quotas and error message. Kindly https://i.stack.imgur.com/ThvMo.jpg requesting to help me solve this issue.