Another question: Can you login with a different account and see if it happens there as well. You might also want to try from a completely different computer as well. The only time I've seen issues like that had to do with the browser and its compatibility settings.
You can try reactivating the Nintex Workflow features under Site Settings to see if that fixes the issue too.
1. I have reinstall again
2. I have reactivate
3. I have run the comparability view
All doesn't work of using methods above.