When it was just Plex Home Theater I purchased it for my Macbook Pro. Now, when I want to use it on my iPad, it makes me sign in (I never had to sign in on my Macbook), treats me like I’m a free user and tells me my use is going to be limited. Btw, we have purchased Plex twice in my household already to have 2 accounts, I don’t want to purchase it a third time.
I don’t recall PHT ever being a product you pay for but regardless, paying for a desktop app would not automatically give you access to the mobile app.
But, if you have paid for the mobile app before all you would need to do is login to the Plex app with those same credentials on another device, as long as the devices all use the same app store.
Ref: https://support.plex.tv/hc/en-us/articles/205556278-Unlocking-or-Activating-Plex-for-iOS
I can’t quite understand what you mean, but I will try to help out.
If you’re talking about Plex Home Theatre (PHT) that you can download from plex.tv site, that is now considered free and the devs went on to do Plex Media Player (PMP) which is exclusive to Plex Pass holders (subscription).
EDIT: Thanks to @Peter_W for clearing that, PMP is now free (Source)
However, if you’re talking about a one time purchase of Plex app for non plex pass holders, then that purchase is only available once per platform.
For example, you “Activated” your downloaded Plex App from an android OS platform, it will only be available within that platform, and when you go to IOS Apple platform, you will need to “Activate” it again.
And don’t forget to sign in on “your” account.
Now concerning your Macbook, i’m no expert on how Apple Eco-system works, but if you activated it on your macbrook, maybe it does not share the same platform as iPad store? I know for android, if I purchase the app on my Nexus Phone, I can also get it on all my android platforms.
Hope I answered your question. Other than that, I’m sorry 
@Ashus PMP is now free for all, see this blog post for more information - https://www.plex.tv/blog/plex-media-player-now-ambidextrous-free-kodi-said/
With this past year of fortification under the hood and the cool new desktop mode, we’re also taking this opportunity to make Plex Media Player available to everyone, 100% free, no Plex Pass required! Now you have no reason not to download and check it out!
@Peter_W said:
@Ashus PMP is now free for all, see this blog post for more information - https://www.plex.tv/blog/plex-media-player-now-ambidextrous-free-kodi-said/
Wow! Great news for free users! Didn’t see that blog! Nice thanks!
I would think that it would still be in the Apple Store, just log into the store ( with the account that you used to actually purchase it) on your iPad and grab it off the cloud.
