Error "The file provided to import is invalid or corrupted"

Issue
When importing a workflow in Nintex Workflow for Office 365, the following error might occur:
“The file provided to import is invalid or corrupted”

Resolution

1. Create a new list.
2. Import the workflow file on the new list. 
3. Review the workflow and check on these actions (including disabled actions):
   • If you have a 'Parallel Branch' action, make sure that at least one action exists in all the branches. 
   • If you have a 'Run If' action then make sure that at least one action exists under this action. 
4. Save the workflow.
5. Export the workflow.
6. Import the workflow into the original List that had the issue.