What is the conductivity reading on the screen and what does it normally read?
When you changed the water did you run it thru a DI tank on its way to the machine or right out of the tap?
If out of the tap you will need to let it circulate for a while and maybe change the resin before you get the DI level for all that tap water down to where the machine will run.
It is best to run your makup water thru a tank before dumping it in the machine.
What happens if you put the sensor in a glass of water that just come out of a new or known good DI tank?
I have done that to get the machine running while the DI circulator pump brings the level down to where it should be. Note: you need to adjust the water in the glass (mix in some dirty water) so that the DI pump is on but the machine still runs.
Never run a 200 but got an RA90 that runs about 2.4 shuts off if it gets above 2.7?? or so, also got some old 90Cs but they do not error and turn off they just slow down a little.
First thing I did is get rid of those little refillable resin tanks and put a 10 by 35 inch bottle on each machine and anouther one on the makeup water source.