Yep, which is why it's a good thing to keep up your quest line as you go. Sometimes you get rewarded in diamonds when you get all the way through and sell your portal. But of you've already sold it and moved on into the next chapter when you get to "sell your portal for x diamonds" you may not be able to do that without rebuilding the portal.....so, hopefully, you will now do the quests as you go? At least that's my advice....good or not, take your pick.
AJ