Train operator Southern has apologised to Uckfield customers who are having problems buying tickets.
Passengers have frequently found in recent months that the ticket office is closed, the platform ticket machine out of order and train guards unable to sell tickets.
It has meant people have to queue on arrival at London Bridge station to buy a ticket.
A spokesman for Southern said the company was sorry that passengers were having difficulties.
He said: “We are working hard to deal with a number of problems.
“Unfortunately, the resident ticket office staff member is on long-term sick leave, and we have not been able to arrange temporary cover for every shift.
“We are now assessing what the best solution will be.
“In the past few days a problem has arisen with the new ticket machine’s fares programming.
“We are working with our supplier to fix this as soon as possible, and passengers should soon see an improvement in the machine’s reliability.
“Conductors’ ticket-selling equipment relies on wifi or 4G connectivity, which is currently very poor along the Uckfield line.
“Service providers are working to increase the extent and strength of their signals, and the situation will improve when we complete the roll-out of wifi on Southern trains next year.”