I have 2 PSN accounts on my PS4. They are in different regions from each other. I have downloaded a game from account B and I want to play the games purchased with it on account A (to get the trophies). The problem is when I switch back to account A and try to start up the game I just downloaded it gives me the error message "Only users who hold a license for this application can start it".
How do i grant a license for this account? Both accounts are logged into the same PS4 and I have no problem with account B playing games purchased by account A. Is there a way to fix this issue?
This is fairly common and is likely due to the primary PS4 not being set. Each PSN account can have 1 primary PS4. If you set a PS4 as your primary PS4 all other user accounts on that device ONLY will be able to play all of the games you download.
It sounds like you have set the PS4 as your primary PS4 for account A and this is why you are able to play the games on account B. You will need to also make this PS4 system the primary PS4 for account B and you will be able to play the games on all accounts then. If you have already set it as a primary system, try restoring the licenses or restarting the system.
If you are unsure how to do any of this, I have a guide here that will show you how to set a PS4 as your primary system.