Problems with mobile devices using data compression apps

We had a report from a using who was posting from their mobile phone of an error message of "Invalid Session". After some dialogue with forum admins the user was able solve the problem, it was traced to the phone using a data compression app to keep the data usage low whilst abroad.We'd like to thank the user for providing us with feedback at every stage of the problem solving process and for solving the problem although they modestly claimed not to be technical.