k40 nozzle change problem - need Help

[stargeezer]

After about three months away, I'm finally getting time to work on my k40. I have installed the 18mm forced air nozzle and new mirrors and this 18mm focus lens, High quality 18mm ZnSe Focus lens (F50.8mm) LSR-ZNSE1850HQ

Now I have just finished aligning the mirrors, which was no problem, but for some reason I Get no output beam from the nozzle. There is a good beam up to the mirror above the focus lens, but tape placed at the focus point shows zero burning. The focus lens is installed with the arch up.

Does anybody have any idea?

Thanks
Larry