Students at Dublin City University have been unable to access lectures and other online facilities due to a problem with the college's virtual learning platform.
The university reopened to students yesterday, with the bulk of learning to take place online.
However students were unable to access the college's student portal through which lectures were to be delivered.
DCU says it is working to resolve what it has called a technical issue.
It also says it has taken down the online learning system temporarily so that it can undergo testing.
It is not clear as yet when the problem will be resolved.
"The technical issue that developed resulted in the system being unable to respond to requests in a timely fashion, at which point the university made the decision to take Loop temporarily offline to resolve the matter," it said in a statement.
It said students were able to attend and access online classes via email and that it had made alternative arrangements to provide them with the access details and information required.
DCU said no student would be disadvantaged as a result of the problem.
It said any classes that were rescheduled, or that have been missed would be provided at a later stage.