Workflow actions on the front-end shouldn’t run asynchronously so I don’t think that’s the problem.
What are the search parameters on this action? It could be that this action is failing to set it to yes
Search for Sessions:count is 0
If I understand, you have the same condition here, it could be either your Search for Sessions:count is 0 is not set up properly, or your Group Widget Nueva sesion NP's Crear Sesion is yes is actually no