You can use the zone guide to start or continue the main Summerset questline. It will show you what your next quest is or if you’ve completed it already.
I had the same issue the other day - couldn’t find Raz to start the main questline so I could start the Psijic line - and it turned out I’d done the main questline on that character. The Psijic questgiver was already available in Ceporah tower.