GE Fanuc Versamax Problem

Hello All. I am having an issue with a Versamax PLC that I can't understand.
I am using a IC200UDR005, with 16 DC inputs, 1 DC output and 11 relay outputs with an expansion unit IC200UEX011 that has 8 inputs and 6 relay outputs.
I recently added a rung to to an existing program that had been working perfectly for years. The rung consisted of a timer, one input and one output. I had addressed the output to one that was unused and was assigend to the expansion unit. When I tested it, everything worked in the logic as expected, but there was no output from the PLC. In fact none of the outputs on the expansion unit worked. I assumed there was something wrong with the expansion unit and replaced it. This did not solve the problem. When I looked further into it,I found that the main unit has the output address %Q00001 as the starting address,so that means it can use %Q0001 thru %Q0012, which makes sense, but the expansion module starts at %Q00017. I cannot change it to %Q0013, which is where the outputs started before I added the rung. When I try to change the starting address to %Q0013, it shows up red because the address will cause an overlap. Why will it not allow me to change the starting address to %Q0013? Previous to adding the rung I am sure that the expansion unit started at %Q0013 because all the existing outputs on it worked.
I am using Proficy Machine Edition software.
Hopefully my explanation makes sense. I do not do a lot of PLC programming so perhaps my explanation isn't 100% clear.

I would appreciate any help.

I'm not completely clear about your total problem but here is what I would suggest. Probably the easiest solution is to just change the existing addresses beginning at Q13.Starting at Q17, make Q13 = Q17, Q14 = Q18, and so forth. I'm guessing here about the rest of my post. Most physical addressing schemes today start at a Hexadecimal boundary. The manufacturer probably built a physical or firmware means to detect when an expansion unit is present or absent. Without the expansion unit present the software probably allowed the use of addresses Q13 thru Q16. That is even if there was no physical output available on your particular model PLC. Again, I'm just guessing, I really don't know for sure. Maybe someone else will be able to give a better answer.

P.S.
I found a manual that has some additional info. See page 20-6 for reference to Q17 being the first Default Output in the expansion unit. It also said that can be re-configured.

Copy and paste from manual:
Q17 Default first discrete output for expansion

I found a manual that has some additional info. See page 20-6 for reference to Q17 being the first Default Output in the expansion unit. It also said that can be re-configured.
Yes, but only on a byte boundary greater than %Q17. This is how it is designed and a function of the OS and chips used.