I am a beginner in yawl,
I try create a simple work flow:
1 task,
1 net variable, with string type and local scope
1 task variable, with string type and input output designation

There is no error, when i check with validate button.

But, when i try upload to resource engine (web), its not work.
And give me blank confirmation..

Sorry, my English is bad.

I could upload the specification and execute it. Are you running the latest version? I have attached a screenshot of my control centre here that shows the version numbers as of today.