One step at a time
If you have not changed any settings since you last used your marker succesfully, do not start fiddling as it is likely this is not your problem.
I fitted a QEV and this seemed to work at first. My marker seemd fine, then it wouldnt chrono consistently until it would just roll the pball out of the barrel. The difference in the change was over about 500 paint from fitting the QEV to failure. We had the reg to bits, then the noid, and it wasn't until someone volunteered the new QEV might not be working did we change that and it worked fine.
So, take a breath, and be methodical about the process of fault diagnosis.
Have you changed or made any major changes to it? Some new components will fail gradually as mine did so think about that. If nothing obvious then...............
Take the reg apart, clean it, lube it in the right place, put it back together.
If this still doesnt work, then move on to another component, of which a good choice would be the noid. Make sure this is clean.
One step at a time try and make sure each part of the Ion is working properly. You'll find the problem eventually.
The Ion aint a complicated beast when you get down to it, so just take it a step at a time to diagnose the problem.
Good luck mate.