How to backup clustered vm's

Issue:

While performing backup of vm's in a Microsoft Cluster environment, the hp dp backup tool is throwing following errors

[61:2052] Bar backup session was started but no client connected in 600 seconds.Aborting session!

[172:157] Virtual Machine 'ERP APP 2': Could not create snapshot ...

Are there any prerequisites or criteria to ve followed for backup of clustered vm's.

We had ensured vm is off and vm is not enabled with fault tolerance prior to performing the backup

Someone, Kindly suggest & guide

Thanks & Regards

Hemant Vaswani