Hi Keesjalink,
not sure what you mean with "issue" ?
GCode Simulator & Printer App for Android is available in the Google App Store already.
It works with many printers (reprap, printrbot, ...), I just did not get feedback from Ultimaker users yet.
Please install the free version and try if the basic printer control works on Ultimaker.
If so, printing with the full version should be fine as well.
https://play.google.com/store/apps/details?id=de.dietzm.gcodesimulator&hl=de
Thanks
Mathias