We are trying to integrate CA APM with CA UIM using the caapm probe however, its not working as expected. 

- UIM 8.51
- APM 10.5

The caapm probe is not supported, this was a beta probe created in 2016 which never went GA. I understand you currently have UIM 8.51 and APM 10.5, the caapm probe only supported up to: CA APM 10.2 and CA UIM 8.4, for more details see the following links: 

caapm v1.01 BETA: http://support.nimsoft.com/unsecure/archive.aspx?id=379 

caapm AC Configuration - Pre-release (Last update June 9, 2016): https://docops.ca.com/ca-unified-infrastructure-management-probes/ga/en/alphabetical-probe-articles/caapm-ca-apm-to-ca-uim-pre-release/caapm-ac-configuration-pre-release 

For UIM -> APM integration please use the apmgtw probe, more details below: 

apmgtw (CA APM Gateway) Release Notes v3.2: https://docops.ca.com/ca-unified-infrastructure-management-probes/ga/en/alphabetical-probe-articles/apmgtw-ca-apm-gateway/apmgtw-ca-apm-gateway-release-notes 

apmgtw AC Configuration: https://docops.ca.com/ca-unified-infrastructure-management-probes/ga/en/alphabetical-probe-articles/apmgtw-ca-apm-gateway/apmgtw-ac-configuration 

For APM -> UIM integration: 

Define the CA UIM alert action to set up native UIM alerting. The UIM alert action sends alert information to a RESTful UIM endpoint. A CA APM alert can indicate a broken SLA, impacted customer latency, or other high value information that UIM cannot access. For more information, please see the below document: 

Define CA UIM Alert Action: https://docops.ca.com/ca-apm/10-5/en/administrating/configure-webview/define-ca-uim-alert-action