Try these:
* Different message (404 not 405), but check out this line of the resolution:
"If you want process automation to run on HTTP , you can rerun the installer and uncheck the Use Secure Communications option."
Unable to log on to ITPAM with http + port 8080 - CA Knowledge
* Was CA PAM configured to use SSL? If so, then your address should be https rather than http.
Try updating this via a config file. (Don't know if this works, but Web Services is present in both SDM and PAM).
"Change the ssl.conf"
Getting HTTP 405 Error on POST request with X509 c - CA Knowledge
* It seems to be tied up with the authentication/security. Is EEM involved?
In any case, is there any more info. in the logs? If you can't resolve at this point, maybe log a CA Support ticket.
Thanks, Kyle_R.