Problem having two user forms open and enabled at the same time on Mac

Hi,
I have one user form from which I would like to open a second user form, which just has images for the user to view while entering related information into the first user form. I know on a PC there is a property that can be set to keep both enabled, but I can't seem to find that in the property list on my Mac.

The only code that I have right now is this (PostTestRun is the second user form with images):

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When this runs, it opens the second user form, but then I can not click into the first user form, or enter anything.

Thanks so much for any help.