Suddenly HP printer disappeared from ATK net.

How do I can trouble shoot and fix this problem?

In the last few days a HP 2200 and HP 4200 printer suddenly disappeared
from the AppleTalk network. One can select and print to both printers in
OSX via IP and rendezvous. The printers do not show in the OS9 Chooser
or in AppleTalk OSX 10.2 or 10.4.2.

The AppleTalk network is OK because I can see the rest network.

How can I trouble shoot and fix this problem?

Magically, we can print to both printers via AppleTalk after restarting
AppleTalk. I attached to the printer with Firefox and selected the
AppleTalk page.

a. Unchecked AppleTalk enable.
b. Apply.
c. Checked AppleTalk enable.
d. Apply.
e. There is long delay as AppleTalk is started.