Hi, I’m having an issue with the Multiple Series Stack option.
When I activate this setting, the number of stacking columns does not update or change. Could you please advise what might be causing this or how to resolve it?

Does it work in other JMP versions? Very difficult to say what could be the issue without seeing the data and what you expect to have.
Normal stack

Multiple series stack with number of series 2 (non-contiguous)

Using JMP > Reshape Your Data > Stack Columns in Data Tables > Example of Stacking Columns into More Than One Column