How can Onify agent access a process?

I try to launch agent script from a workflow. When I use onifyApiRequest in async mode, the agent seem not be able to signal to the process when the script is completed. The agent script get executed, but the flow gets stuck waiting response of agent task. I get this error to Onify app log:

DEBUG client (403): Agent user agent do not have permission to access process (06bdead772f34b23913e79f5ccaa7b7e)

How can I give priviledges to agent for accessing the process data and letting it to signal the process when agent task is completed?