upgrade to 9.4.0 issues

[Hisham Al Saad]

Hi,

We have 4 DNS servers ( 1 primary and 3 secondary) running BIND 9.2.6.
We upgraded them to BIND 9.4.0. After the upgrade, any zones changes
made on the primary server do not replicate to the secondary servers,
so the secondary servers will not notice the changes. If i downgrade
the primary server back to 9.2.6 everything works fine
Currently I have the secondary servers running 9.4.0 and the primary 9.2.6.
Is there any changes i have to do on the primary to have it update the
secondary servers after upgrading to 9.4.0. ?

Please advice,
Thanks,
Hisham