Hello,
The issue of non charge neutral system has been discussed many times here, see for instance this older post.
My opinion is that if you use a non neutral system on purpose, you better have a really good reason to do it, as well as some solid proof that what you do makes sense.
In most cases, MD systems using Ewald/PPPM methods must be neutral. It could be that non charge neutrality is the reason behind the “out of range” error you have, but it could also be that the rest of your simulation is wrong. With almost no information on your system and input, it is impossible to say, and ionic liquid can be tricky systems to simulate.
Best,
Simon