We have a Nintex workflow which integrates with Nintex forms. It has been failing to start the flow for no reason. There are no error logs in the ULS logs or in the Nintex logs.
The New Request Initiate and Build Task List v3 workflow has ended unexpectedly for Test.
Workflow New Request Initiate and Build Task List v3 was canceled by System Account.
Have you looked at the following: Unable to publish or run workflows after installin... - Nintex Community
We had to implement both sets of changes to get our workflows functioning again.
@tes same error occured on our client environment last week, and the issue was due to security patches installed on SharePoint server. refer to below articles:
And make sure to reset iis and timerjob.