Hello it appears that Nintex workflow has stopped triggering automatically since we added a remote event receiver on the list. I tried removing nintex workflow app and re-adding it. Also re-published the workflow but no luck. Starting the workflow manually works as expected.
@LambrosV May I suggest contacting Microsoft about this. Since you posted this in the Office365 space I am assuming this was done in the cloud. Not 100% sure how you did that, but that is my assumption based on this being posted here.
Triggering a workflow automatically is done via the SharePoint services for a new item. If its not being triggered, ensure the user creating the item has the correct permissions and that the workflow is published to start on new item creation. Also becuase it does run when triggered manually suggest that something else may be causing a problem outside of Nintex itself.