With regards to the New User Email Setup Plugin, yes there are issues with this (as discussed in
this thread). It's not ClassiPress specific as I have tested it on the default theme as well with no luck. I have logged a ticket with the development team to see if there is anything they can do to get it working, however it may be that we end up recommending a different welcome plugin. You may want to check the thread I linked to above for examples of what other people use instead..