an error occurred when the workflow was being created. try to save the workflow again

So I got this Error after adding my custom activity to my workflow and tried publishing:

An error occurred when the workflow was being created. Try to save the workflow again.


I tried everything:

Roll ups and editing web.config but no help. My other Workflows worked fine, to me that meant my new custom workflow is up to shebert...


Please check:

My class and namespace was SendEmailActivity :

Changing my Namespace to XXXX.SendEmailActivity

This fixed it:

Not sure if it was because the two (nmsp and class) are the same or because Starndard CRM clushes with these.

Name things properly