First of all make sure that you're trying to restore access to the right app, champ.
If you actually used to have Tabs&Chords
app, then you can't restore the Tab Pro
To know for sure you can visit this page with apps' descriptions ---> http://app.ultimate-guitar.com/apps/
OK, there are 2 ways to restore access to Tab Pro app on your iPhone: 1.
Log in with your Ultimate Guitar account. If you had access in the past and were logged in, then access to Tab Pro got attached to your Ultimate Guitar account.
If you never logged into the app or don't remember the password or never new that you could log in at all, please see the next option.2.
Restoring with your Apple ID.
1) Open the app.
2) Go to Top100
3) Open any tab
4) Hit "Restore"
and enter the same Apple ID, that you used to make the purchase.
Note: Your Apple ID is not the same as your Ultimate Guitar account, please don't confuse them. Also, your Apple ID password is not the same as your Ultimate Guitar account password. If you don't remember your Apple ID password, please use "Forgot Password" option in your Apple ID account. If you don't remember your Ultimate Guitar account password please refer to the following article: http://support.ultimate-guitar.com/knowledgebase/articles/514271