The syntax:
polyspacesetup('install')
Is immediately available only from R2021a.
In R2019a, you have to do a few steps prior to executing this function. In particular, you have to navigate (cd) to a specific folder polyspaceroot\toolbox\polyspace\pscore\pscore\. Here, polyspaceroot is the Polyspace installation folder, for instance, C:\Program Files\Polyspace\R2019a.
See R2019a documentation: https://www.mathworks.com/help/releases/R2019a/bugfinder/ug/integrate-polyspace-with-matlab-and-simulink.html .
