Translink customers have experienced problems with the company's mobile payments app for the fifth consecutive day.
The company recommended on social media that customers put their phone into airplane mode to display their ticket as "a quick fix".
It is encouraging users to buy their tickets outside of peak times or to consider other ticket options.
A spokesperson said the issue was UK wide and due to unprecedented demand.
Translink also tweeted information from the app's supplier saying that some transactions are going through but acknowledging that problems continue:
"Intermittent latency spikes result in a temporary slower response and in connection errors for some users, however the apps are more stable, remain in service and transactions continue to go through."
The mLink app allows passengers to use pre-paid tickets on public transport.
#mLink Some users are still having difficulty this morning using the mLink app. This is a UK wide issue affecting rail passengers across the UK. Apologies for this ongoing issue & again thank you for your patience. https://t.co/fAInBLJ6QV— Translink (@Translink_NI) September 7, 2018
"We continue to work closely with our mlink app supplier to resolve this issue as soon as we can," a Translink spokesperson said on Thursday.
"We will keep passengers updated on social media channels."
Translink said on Wednesday they do not know when their mobile payments app will be fixed with customers taking to social media to vent their frustration at the difficulties with the mLink app.
The company said the problem was not directly related to the start of the new Glider buses in Belfast.
Translink ticketing manager Simon Hunter apologised to customers.
He told the BBC the technical problems were mainly at peak times, and insisted that customers double-charged for tickets would receive refunds without having to fill out any forms.