App didn’t work on my iPhone – Mento - Frontback Collage & Blend of Photo, Video & Emojis Camera Review

Downloaded the app (twice), “allow access” (to camera) button doesn’t do anything. To dev: I’m using an iPhone 6 with iOS 12.2.
Review by Makazoid on Mento - Frontback Collage & Blend of Photo, Video & Emojis Camera.