Final Draft app won't update on my Ipad

I was having issues with DropBox on the Final Draft Writer App on my model # ME216LL/A Ipad so I contacted customer support for Final Draft. They instructed me to uninstall the app then reinstall it. I uninstalled without a problem, but when I tried to reinstall it, I get the message "Unable to Purchase: "Final Draft Writer is not compatible with this Ipad". WTH? I forwarded this along to the FDR support who responded with this:

"Given that this message begins “Unable to Purchase,” it sounds like the App Store is prompting you to re-purchase the FD Writer app, which suggests that your App Store app is not currently logged into the same account that you had used to purchase the app. You’ll need to log into the same account in order for “Download” or “Install” to be the available option, instead of “Purchase."

If you’re certain that you’re logged into the correct App Store account, I’m afraid you’ll need to contact Apple App Store support to figure out what’s happening here.

As we understand it, the App Store policy is to make legacy builds of apps like ours available to users who originally purchased the app on older iOS versions, precisely to avoid situations like this. In the meantime, we’ll be checking in with Apple on our end to ensure that this is indeed still the case.

Sorry for the inconvenience. We had no intention of misleading you, if Apple now no longer allows the reinstallation of this older build. If it turns out that Apple has instituted some new cut-off point for reinstalling legacy builds of App Store apps, this would be just as much of a surprise to us as it is to you."

So I tried to download the Apple support App and I get the same "not compatible with this Ipad" message.

Frustration has set in. All I want to do is be able to write scripts on this Ipad. This was the sole reason I bought it. Any advice?

Thanks.