I ran into this issue as described in VMware KB2140539 where requesting an XaaS (vRealize Orchestrator) blueprint fails with:
Failed to retrieve form from provider
The KB describes it occuring when “more than one VMware vRealize Orchestrator instance is configured for different tenants“. The issue I faced is not the same – in my case, I had the system default tenant configured to use the embedded vRO, and the customer tenant configured to use the system default (which would be the embedded vRO!)
The article itself does not give a work-around for this issue, but it’s possible to resolve it by editing the customer tenant Orchestrator Server configuration (Administration > vRO Configuration > Server Configuration) to use the external load balanced URL for the appliances (or for a PoC/small deploy with a single appliance, the appliance URL).