Trouble Setting New Tax Rate on TEC FS-1450

Please help!

I am trying to change the tax rate in my TEC FS-1450 to 8.0%

First, this cash register works perfectly with the 7.0% tax rate currently loaded.

The procedure I have followed is:

Status Clear Operation (Status-C prints on receipt)
Turn key to "Set" position (no problem here)
Enter the number zero (no problem here)
Press the "TM1/M" button (no problem here)
Press the "ST" button (HERE IS MY PROBLEM...I get a solid error tone)

The next step SHOULD be
Enter eight point zero [8.0] on the keyboard (the new tax rate)
Press the "AT/TL" button

I have ran every single "Z" report available.
I have tried a Status Clear Operation while pressing the zero [0] key upon power on.

Any ideas? Can anyone help?

Thanks!!!!