VMware Site Recovery Manager: VM Protection - Network Not Configured

So that title is a mouthful, but I came across an issue for a customer today where network mappings within SRM were not functioning correctly when attempting to configure protection for virtual machines. To cover this off quickly, the environment is running vSphere 6.0U3 and SRM 6.1.2. The scenario was that we’d previously (a few months ago) configured all of the mappings in SRM (Network, resource, folder, etc). We then created a new protection group, and created a recovery plan for this particular protection group.