TFS 2015 vNext Gated Check-in builds are “Waiting

Question

We are trying to use TFS 2015 Gated Builds. The trigger hooks in correctly, and the build gets created, but it never gets picked up by any agent. Non-gated builds start fine, and if we manually restart the gated build, that runs fine too. But the gated build (the important one), just sits there saying "Waiting for an agent to be requested" and "Waiting for an available agent":

No logs get created in the _diag folder for these builds.

EDIT: Added screncap of agent:

Answer 1

Check the table tbl_BuildAgent in TFS project collection database. Sometimes an agent entry may be causing this issue.