View Ranger App

I do a lot of walking and wanted an app that would record my walks on OS maps. I found View Ranger that looked perfect. Downloaded it to my TAG 45 but I get a message on watch saying to download the app to my phone. I already have the app on my iPhone 8plus but it doesn't seem to recognise it . is this an android/iphone problem does anyone know? I presume the app on my phone is for apple and the one on my watch for android and never the twain????
Thanks in advance for any help

why not get android phone .. its easier lol

Just been in touch with View Ranger support and as I thought won't work with my combination!! Arghhhhh!

Have thought about it TGHC45 but will stick with it for now lol. Ive got apple watch so will just have to use that when Im out walking.