Test feedback is generally not very helpful. Look at it as a checklist rather than reasons for failure.
In addition to the checks listed in your screenshot, make sure you’re not using any hard-coded values and that the workflows you’ve created match what was asked in the exam. Note that a list or array of data can be added to the Config file with delimiters.
In general, avoid workarounds. If you’re having trouble getting something to work, find the simple solution if possible. Also, maximize your credit wherever you can. Extra credit is given if you can create a solution using Visual Basic rather than built-in functions. For instance, if you build and update a datatable with visual basic code rather than activities, you show a proficiency in the underlying language, and can provide more config data for flexibility in your workflow.
Honestly, though, the main thing that I think gets most test-takers is hard-coded values. There is nearly always a way to get your hard-coded data into the Config file rather than typing it in directly.