Reboot greyed out

I'm using the current version of Teamviewer, and been using it for some years, with Win7.

The remote is also on Win 7 and all's running very well. Lately I require to reboot the remote PC more often and find it rather cumbersome to wait for a new code via email. I can see the reboot option but it's grey and therefore useless.

Surely I'm missing something, where am I going wrong?

Ant tips most welcome.