WhatsApp issue migrating from 4s to 6

[Advancer]

Tried backing up my wife's iPhone 4s to iTunes and restore it into the new iPhone 6 and realised a lot of apps had issues.
Especially WhatsApp whereby the messages are all not backed up.
Is it an ios8 comparability issue?
Her 4s is still on ios7.

 

[szeli]

iOS7? have u tried iCloud backup? it should work.

 

[Advancer]

But she has many photos on her ip4s and intends to transfer them to the ip6. Only way to transfer all is to use iTunes as the backup file is bigger than the icloud 5gb free.
Correct me if I am wrong.

 

[szeli]

a new update for whatsapp just released. nw when I navigate to e chat backup function in app it doesn't show "not compatible with iCloud in iOS 8."