Install .IPA file through computer?

[AppleFan22]

I've got an .IPA of an app which is no longer available on the app store (although it was until only recently), which I'd like to reinstall onto my iPhone.

Is there any way of doing this through a computer without having to install iTunes 11? The Applications page has been removed in iTunes 12+ so that's no good...
[EDIT: I've tried installing iTunes 10 (as that's what's available on apple.com) on the Windows but it keep failing...]

I have access to both macOS and Windows if that's useful...

 

[Intell]

You can use iTunes 12.6.3 or with the latest version of iTunes drag the IPA onto your device's summary screen.

 

[AppleFan22]

You can use iTunes 12.6.3 or with the latest version of iTunes drag the IPA onto your device's summary screen.

I've just installed iTunes 12.6.3 and done it, it installed it but then when I tried opening it it told me I have to install it through the App Store... Any possible workarounds?

 

[Intell]

Where and what is the exact error message?

 

[AppleFan22]

Where and what is the exact error message?

Exactly this, on the iPhone:

Note that iTunes didn't provide any error messages or anything when copying the app.

(Trying to get the old Snapchat back by any means necessary!!)

 

[Intell]

Where did you get that IPA from? You can only install an IPA if it is one that your purchased with your Apple ID. If it is a random one you download from the internet, it will not work. You must use one that you previously saved using iTunes.

 

[AppleFan22]

Where did you get that IPA from? You can only install an IPA if it is one that your purchased with your Apple ID. If it is a random one you download from the internet, it will not work. You must use one that you previously saved using iTunes.

Ugh that’s a pain. It was a random internet one haha!

By that logic, if I can find an .IPA in my backup files somewhere I that should work instead?

 

[Intell]

Yes, that one should work.

 

[AppleFan22]

Yes, that one should work.

It worked! Well, sort of... The app itself installed fine and I can open it, but it won't let me log in, probably because the one I found is such an old version... Now to try and find a somewhat more recent one!