Hi,
you missed the acls:
you need the following:
Router A
conf t
no access-list 101
access-list 101 permit ip 192.168.15.0 0.0.0.255 192.168.200.0 0.0.0.255
Router B
conf t
no access-list 101
access-list 101 permit ip 192.168.200.0 0.0.0.255 192.168.15.0 0.0.0.255