We are happy to help either here or at G3. Just to confirm, you have:
1. Are playing Tutu, not BGT or BP-NeJ-etc.-etc.
2. had Jaheira in the party
3. Met with Seniyad, and gotten the quest from him
4. Found Beador and rescued him (or at least tried)
5. Gone back to near the Tree Fort and encountered Andarthe, NOT Amarathe (there are two ArchDruids, one who lives at the top of the Tree Fort in vanilla Tutu and one who tries to whup you in BG1NPC Phase2(Quests))
6. Killed Andarthe and rescued Maretha (you get a rep + or - from the final encounter with her)
7. Returned to Seniyad, and found him responding as if you had never gotten the quest.
Is this correct?
If it is, and you have done all this, I m not sure what is wrong -- but the way to finish the quest is to set the following variable:
CLUAConsole:SetGlobal("X#JaheiraSen","GLOBAL",31)
and then talk to Seniyad again. He should give the final talk, closing the quest and leaving the area.
The next version of BG1NPC will have more journal feedback and some closer scripting of variables to make this quest run more smoothly.
As a side note, anyone reading this post to troubleshoot their own Jaheira Quest challenges, please be aware that any quest in any mod that delivers reputation gains or losses can result in a neutral quest character suddenly leaving the party unless you have used the "happy patch". The safest way around this happening for Jaheira in her Quest at the present time is to use BG2-Tweaks or SCS (if it's 3e Ruleset Druids component still does this) to reset Jaheira to Neutral Good. This is because neutral NPCs will try to leave parties that reach extremes of good or bad reputation (19 or 20; I am not sure about the low delimiter).