Many callers to the Digitial COVID Cert helpline are waiting well over 90 minutes to speak to an agent.
The Department of Health has confirmed there's been a "high volume of calls" since the line opened yesterday.
For now, officials are asking people to only call if they're due to travel shortly.
Many of those who've been trying to get through have expressed their frustration about being unable to get through.
The EU Digital COVID Certificate (DCC) is proof (in digital or paper format) that you have 💉been vaccinated against COVID-19, 🧪received a NEG test result or 🩺recovered from COVID-19 in the last 6 months.
Two helplines now open:
☎️1800 851 504
☎️1800 807 008
— Hildegarde Naughton (@1Hildegarde) July 20, 2021
The helpline centre has just 55 people answering calls at the moment, but it's expected that will increase to 90 agents by the end of the week.
The line collapsed under pressure yesterday and managed to handle just 1,160 calls.
Callers will now be advised by an automated system if the wait time is expected to be over 90 minutes.
The line is the only way for people who've recovered from COVID-19 to get a cert, and is also available for those who've been vaccinated but yet to get a cert.
However, Junior Transport Minister Hildegarde Naughton says the helpline should only be used by people with urgent queries.
She said: "I would ask people to be patient and only contact that helpline if you're flying out and you need information about your cert."
Two helpline numbers are now available - 1800 851 504 and 1800 807 008.