HACMP version for AIX 6.1

Hello.

We are using AIX 5.3 with HACMP 5.4.1.

At this moment AIX and clustering are using 2 servers.
A third server is added.

It does not seem to work with HACMP.
Are there any controle checks?

Thank you if you could help.

Regards,

Ynze van Aken
Netherlands