Some students tried for hours to get onto the site but could not log on while others were successful and eventually received their long-awaited results.
Dozens of parents took to Facebook to complain, many saying alternative arrangements should have been put in place for such an eventuality.
A spokeman for the college said it was hoped that the issue would be resolved by early afternoon and added: "Huge apologies for this issue on what is such an important day for our learners.
"We have been working extensively with the relevant technical teams to try and get the technical issue with Cedar resolved.
"We are also looking into alternative arrangements for results delivery.