A network problem at Manx Telecom has left about 4,000 homes and businesses on the Isle of Man without internet access for almost two days.
Benefit and pension payments using the government's MiCard service have been disrupted as several post offices have been without a broadband connection.
The outage began on Monday evening and has affected people across the island.
The firm's chief executive Gary Lamb said engineers were working "flat out" but had not yet identified the problem.
An attempt to fix the issue overnight with a "hardware upgrade" failed to work, a spokesman added.
Mr Lamb said the company was looking at "alternative short-term arrangements" to help customers with "critical broadband requirements".
Affected businesses have been unable to accept card payments, which rely on a network connection.
Eight post offices have been impacted and customers collecting benefits and pensions have been advised to use the Douglas facility on Strand Street, which has not been affected.
The issue has also left some customers of Sure, which uses Manx Telecom infrastructure, without internet access.