Strange opacity behaviour with a 'Pop Up' on a screen

Hi everyone!

Long time listener, first time caller :wave:

I have a bit of a strange situation happening in my Figma file. I have mocked up an app screen for an iPhone and sought to pull a permissions ‘pop up’ box that I made to sit over the top. However this ‘pop up’ keeps becoming transparent when I pull it over the top of my frame.

I’d love some insight from people much smarter than me at Figma as to why this may be happening and thus how I can fix it.

Thank you in advance!