We use 'on' for the hardware and means of communication/channel of information: on TV on the BBC on Netflix on the radio on my phone on the web on the internet on Skype We use 'in' or 'with' for systems, software and languages.

Think of "on ..." more as a phrasal part of English :) If we want to refer to actions performed ON machinery or equipment, we say "playing on the phone" "researching on the computer". So, you would say "monitoring financials on the ERP system". However, use the preposition "in" for actions to objects with 'limited' spaces - sitting IN the bath, playing IN the garden etc. I hope this helps and if you need any help with prepositions, I will be more than happy to help:)