Question:

A user has been assigned a workflow task that they would like to complete on Vault Mobile. However, the task is only appearing within the SEE ALL tab of the mobile application's task screen. What is the reason for this behavior?

Answer:

Legacy Document Workflows and Object Workflows are not compatible with Vault Mobile at this time. If a Legacy Workflow is re-created using One Workflow functionality, it can be configured such that it is compatible with Vault Mobile task completion. 

Related Documentation:

Vault Help Documentation: Using Vault Mobile - Tasks