POS360 has been updated! You should now be using Version 3.5.5.
Please visit this link to download the new version: http://officebackend.com/apps/pos360/index.html
If you see an "untrusted enterprise developer" error," go to the Settings app --> General --> Device Management or Profiles. Select Zuza and choose Trust.
If you need help, give us a call at 408-295-8360.