Stretch vSAN cluster from SDDC manager fails at the task "Configure vSAN Stretch Cluster" when operation reserve is enabled on the vSAN cluster from vCenter side.
SDDC Manager 5.x
SDDC Manager 9.0.x
Verify if operation reserve is enabled on the cluster which is being stretched under vSAN configuration
Disable operation reserve under reservation and alert tab under vSAN configuration at cluster level.
Configure Reserved Capacity for vSAN Cluster