A customer reported an issue with invoking a Modify User TEWS call didn't work. Working with the customer we learned it was for that no actual changes were part of the Modify request. This caused nothing to show in View Submitted Tasks despite that Modify XML request received a valid Transaction ID.
I would like to explain this in more insight:
There is a flag (checkbox) on any Modify-Type task that by default is unchecked. This checkbox, if selected will have the product generate and process the events even if no input of any actual changes. By is unchecked (as is by default) it will accept the task but not process anything. In that case nothing will show in View Submitted Tasks. This setting is per the task and is equal whether submitted from user interface or TEWS.
The Transaction ID in the TEWS response is basically only an acknowledgement back to the client that your task was received by the server. It is not an indication of processing or of success. It's an indication of receipt only.
Most customer don’t turn on this flag. However, some reasons to still turn it on could be if you have some triggers along your modify process that don’t depend on any input, for example some custom code, some PX to trigger something which you may still want to invoke. But the downside of checking it would be to have the product process possibly unneeded transactions. Usually it’s recommended to try to avoid checking it.