The Tunisian outfit held a 4-2 first leg lead from Sousse and Kennedy Boboye's men required at least two goals without reply to progress but they bowed out 4-3 on aggregate.
And the Peace Boys midfielder admits they did not do enough to advance while apologising for the below-par performance in the crucial reserve fixture played in Kano on Sunday.
"We are disappointed not qualifying for the next stage of the Caf Champions League," Elijah told Goal.
"We were close to qualifying but we just did not do enough to get the two goals we needed. We started the game well and created some chances though we managed to score a goal.
"I also think that we were just not lucky enough at some points in the game because we put in great efforts in getting opportunities to score especially in the first half, but no way.
"Generally, I feel that we could have done better to get the second goal which would have helped us qualify. Now, we must blame ourselves for crashing out at this stage.
"Apologies to the fans of Plateau United and the state government who expected us to qualify. We are indeed sorry for letting them down."
Ahead of their Caf Confederation Cup campaign, Elijah assures they will learn from their early exit, while he believes the exposure they have gained will propel them in the competition.
"It is our first outing in the Caf Champions League as a club and great exposure for many of us as players. We have taken many lessons from the competition," he continued.
"We have the Caf Confederation Cup ahead of us and we must prepare better for opponents that we will get at the draw.
"We will also make sure that we correct the mistakes we made and I think the experience that we have in the competition now will help us a lot."