TeamCity - Unmet requirements: DotNetFramework4.5_x86 exists

Question

I am very new to TeamCity and currently have a problem with an incompatible agent:

Unmet requirements: 
DotNetFramework4.5_x86 exists

Does anyone know how to fix this? Do I have to add a reference to .NET 4.5 somewhere?

Any advice appreciated.

Answer 1

We had an agent that was working fine, but suddenly stopped with the same unmet requirement from the original question.

I tried restarting the agent service as @arcain suggested, but that did not work. So I went to the TeamCity "Agent Summary" page and disabled and then reenabled the agent and it started working again.