When you trigger a reconfigure request using API / Powershell / Custom Workflow on an environment which was recently patched to any of the released vRealize Automation 7.4 patches , they would fail
Exception would be as follows
Error Message: [Error code: 42300 ] - [Error Msg: Infrastructure service provider error: A server error was encountered. Value cannot be null. Parameter name: value] dynamicops.api.client.ApiClientException at dynamicops.api.client.ClientResponseHandler.handleResponse(BaseHttpClient.java:316) ~[iaas-api-client-7.4.0-SNAPSHOT.jar:?] at dynamicops.api.client.BaseHttpClient$1.handleResponse(BaseHttpClient.java:164) ~[iaas-api-client-7.4.0-SNAPSHOT.jar:?] at org.apache.http.client.fluent.Response.handleResponse(Response.java:90) ~[fluent-hc-4.5.5.jar:4.5.5] at org.apache.http.client.fluent.Async$ExecRunnable.run(Async.java:81) [fluent-hc-4.5.5.jar:4.5.5] at java.lang.Thread.run(Thread.java:748) [?:1.8.0_161]
Though this request fails from vRA perspective on it's console , it does go ahead and performs re-configure operation on VM.
You would experience this issue only if there is a encrypted custom property in the blueprint
This bug is being fixed in upcoming 7.4 patch release.