Step-down DC/DC converters 0 V output voltage
While debugging a circuit, there are a lot of things to take care.
Talking about the CE pin. Checking on the datasheet, see Logic levels and current levels that needs to be taken care off.

The nominal current it requires is 0.1 µA. So 100k would not cause a problem.
Further moving on, in the circuit, the values chosen are same as that of Datasheet applications. So component values will not be a concern.
As @winny said in the comments, working with IC at 6V is dangerous with 6.5V max rating. Slight glitch while turning on the supply, IC gone!
If IC is the problem, while replacing, put a Zener diode at input for protection feature.
Although Check the following steps:

Check all the connections at the IC pins. Voltage levels should be there as pin specific. Continuity of the circuit path throughout the setup. (Most important step. Majority part of debugging gets solved in this.)
If using voltage divider circuit. Make sure the voltage at the CE pin is within high level values.
If oscilloscope is available, Check the Lx pin, PWM type waveforms should be there.

After checking out these things, please comment with the values for further debugging if required.