Congress is required to call a constitutional convention when requested by 2/3 of the State legislatures. It's really pretty simple to understand.
It is easy to understand the Constitution says they "shall" call a convention. It has never been determined if "shall" means "must" or "may." It says states shall provide full faith and credit and extradite fugitives, but there is no way to enforce these provisions and states have not always followed these "requirements."
I can't imagine Congress not following this provision, but I never thought states would refuse to extradite fugitives, either.