First of all:

if you bought directly on JAZZHEAVEN.COM - that login will NOT work with the APP. 

Purchases on and APP purchases are two completely separate things.
See here why. 

Next, if you bought the APP version, but you don't see your purchase in the APP:

Please try deleting the JazzHeaven app and installing it again.

IMPORTANT: we have several apps in there - so you MUST download/use the app that you purchased with!

=> our different apps have the SAME videos available for purchase inside the app. 
=> BUT: the APP TITLES will be different.

One geared towards GUITAR players, another for PIANO players, etc. 
and the MAIN JazzHeaven app will NOT have any instrument-specific title.
The main JazzHeaven app in the APPLE APP STORE has the following title: "Jazz Licks Technique Harmony Improvisation Lessons" 

The main JazzHeaven app in the GOOGLE PLAY STORE has the following title: "Jazz Improvisation Lessons" 

===>>> Again, you MUST access your product in the JazzHeaven app that you purchased in! 

Otherwise your product will not show... 
=> TIP: check your EMAIL RECEIPT for the app title of your purchase (e.g. "Jazz Guitar Lessons") 
- then download & use the JazzHeaven app with that EXACT TITLE!)

Once you re-install the app: hit RESTORE PURCHASES and it has to show up...

If the RESTORE PURCHASES button at the bottom does NOT do the trick: you could just "act as if" you want to buy the SAME product AGAIN.

YOU WILL NOT BE CHARGED TWICE! No worries. :) Just click as if you want to "buy" the video again!

Apple/Google would then realize you ALREADY bought it - and point this out to you - and you would NOT be charged a second time and could just access the product.
IMPORTANT: you must do this in the SAME JazzHeaven app you initially used for your purchase! (See info further above on this.)
=> If you try to "purchase the same product again" in ANOTHER one of our apps: it then WILL charge you twice.

(Since you then bought a 2 products in TWO different apps...)

If this happens, you can get a REFUND:
APPLE APP STORE: you must contact APPLE directly. See HOW-TO LINK. We can unfortunately NOT initiate that refund on our end.
GOOGLE PLAY STORE: for the first 2 hours: you can do it yourself: HOW-TO LINK. After that: contact us, and we can initiate the refund. No problem.

Lastly: if you are talking about the 12-MONTH ACCESS version for the APP:

In order to manage the access permissions for that, the APP will ask you create an ADDITIONAL username/password for that.

(Which is NOT your Apple ID & Password!!) And there is a help link, in case you should not remember that one...)

More APP FAQ here.