The new government website is expected to reopen tomorrow following a large number of applications.
Within hours of the new website going live this morning, those looking to book a coronavirus test online were met with the message to "check back later", after being told: "You can't currently register for a COVID-19 test."
Earlier, the website displayed a message that Friday's allocation of home-testing kits had already been reached.
The Government had rolled out testing to all essential workers and any members of their households who are showing symptoms of COVID-19 from today Friday, April 24.
Employers can now register and refer staff who are self-isolating, while employees are able to book a test directly for themselves or anyone in their household who has a high temperature or a new continuous cough.