Richo Aficio - wheels locked

This isn't a technical question - I mean the literal wheels on the bottom of the printer appear to be locked.

The tech was out last week. He moved the printer, and when I tried to move it back, I discovered that it would not move. Previously I could move it easily by myself.

I don't want to call the tech back out for this.
I'm sure there must be some simple mechanism somewhere that will unlock the wheels, but nobody can find it.

Please help!
Thanks -