When calling a web service, you do this by calling it with a 'Call webservice' activity in a microflow. In this activity, you can select the parameter to be passed to the webservice. This parameter should be in the scope of the microflow calling the web service, so should have either been passed to the microflow as parameter, created in the microflow or retrieved by the microflow. So for example in your case you should have a list in the microflow which you somehow created/obtained (for example through a retrieve action) and configure the 'Call webservice' activity so the list is passed to it as parameter.
Are you doing that, or trying to get the list passed to the webservice in a different way?
I have work around by creating new object of any dummy object and attach it to the list I want to map ,but I think the micro-flow should works. if any one has an answer ,please send because I need it as soon as possible, thanks in advance.
I ran into a similar issue. Did you have anything in the "Association to parent" drop down within your object mapping settings? I found that if you have an association selected even though you select to "Call a microflow", it will still try to use the association and the microflow won't be triggered. I had the same idea of putting breakpoints and they weren't being hit for me either. Once I removed the associations for all the mappings involving microflows, my breakpoints worked showing that the microflows were being utilized.