Unable to download app. Not available at this time

I have IMovie on my iPhone 6 and had it on my iPad pro, too. The app store had it queued with a couple of other apps for "update" so I clicked on "update" for them, individually. It updated every app except IMovie. It starts to update (the black progress circle like a clock, in the screenshot I've attached), but after about a minute I get a small white window saying what is in the title of this question, above ^^ (in the other screenshot I've attached). This has been going on for a couple of weeks, every app will update except IMovie. I have uninstalled it from the iPad and tried to reinstall it, but I get the same white window with the same message..