Any idea what was "messed with"?
Is the twine threaded correctly? (Should be a diagram in the twin box.)
Did you cycle the netters once with the twine tied to the side, so the twine discs in the knotters have grabbed the twine?
Are the needles timed correctly?
I hope you have an Operator's Manual, 'cuz there's a wealth of knotter troubleshooting info there.