I also have this issue and can't resolve it.
The ICA cert expired, which caused all gateway SIC certs to expire. I've renewed the ICA cert and re-established SIC to all gateways. Everything is now working except for IPS reporting the error that it is not responding.
#ips stat says it's running and has the latest database version.
I've run #ips off followed by #ips on. Still getting the error.
I've unticked IPS, installed the policy, ticked IPS and installed again. Still no joy.
What else can I try to fix this error?