Hey there Holywiez!
We can’t check your character quests via Forums, so I am afraid we can’t give you any specific guidance, but considering your description of the problem I think there may be just a bit of confusion.
“We Meet at Lights Hope” is not the end of a questline, but one of the first quests of the Paladin class hall campaign. The quest also is not offered in the Sanctum of light, but in Dalaran directly by Lord Maxwell Tyrosus.
My suggestion to start would be to double check the class hall campaign quests via the link above, and make sure that you have actually completed all the pre-requisites for We Meet at Light’s Hope, and double check if you have any class hall quest available in Dalaran.
If you are sure you have all the requirements for the quest though, please open up a ticket to our GMs, and they’ll do their best to look into this for you as quicklky as possible ^^