Check error.log and project-dwre.log for detailed messages.

If configured Replication Agent is not valid - check if Replication bundle is active in OSGI Console.

If the Replication bundle is not active and missing dependencies - check if AEM 6.4.5 Service Pack is installed.

Go to the OSGI Console and verify there is "Demandware Client" config for instanceId, configured in Replication Agent. Verify that Demandware Client config is valid. The mandatory properties are Instance endpoint ip or hostname, Asset download endpoint and Instance id.

Note! Invalid configurations will be listed in /system/console/configMgr. To view valid configured clients go to Components, search for "DemandwareClient" and check the status=active.

Go to OSGI Console and verify there is Demandware Access Token Provider config for instanceId, configured in Replication Agent.

Verify that the system user, configured in Agent dialog exists and has jcr:read permissions to replicated content AND jcr:read and jcr:write permissions to it's profile node (in /home/users/system/demandware/....

Check the users from the sample content. To see what access rights are required.

Verify dwreSite property is configured for the page (or parent) and such Site exists in SFCC.

Check if your template is listed in the list of considered resource Types in the Demandware ContentBuilder Plugin for Page > Content Asset transformation (see Configuration).

Verify WebDav username and password configured in Demandware Client. Verify that the dwreLibrary property is set in /content/dam/path-to-asset or any parent node and that the specified library exists in SFCC.

Verify "DAMAssetPlugin" OSGI config. If needed, modify the relative path of the WEBDAV share for static assets.

The OCAPI is a ReST interface. You gain a lot insight if you eavesdrop on the connection.

The conversation between AEM and SFCC is encrypted however - though there is a nice hack to eavesdrop with an http proxy anyway.