"No agent can build this job" is shown even when eligible agents are idle

Deployment steps that use "Maven 3.2" are showing "No agent can build this job".

Facts:

1. A compatible remote agent is available
2. Remote agents are all marked as 'idle'
3. This functionality was working fine yesterday.
4. Have not done any reconfiguration or deployment of this task.
5. Issue persists even after a reboot.
6. This is preventing all builds from completing.

Sorry - missed the screenshot where it was showing Maven 3.2 being the "required capability" that was failing.