My dads HTC Desire A8181 phone can't use google play due to varification problem

my dad has a HTC desire A8181 and he has a problem where he can't log on to google play.

It happend like this: 2 years ago my dad got a message that he had to log in to google play on a Google account but he forgot his password so he did nothing and just diden't log in. now he wants to log back on to his play store and download an app so I instald another Google account and that worked. Now his phone gives a popup every time i try to install an app that says

verification required, you have to log on to your google account (translated from dutch)

the app does not install and it says that every time, how can my dad log in to his account to verivicate tht and solve the problem? or is there another solution to solve this and install apps?