I am currently having the same issue but I have found no help for the solution.

I am honestly at my wit's end with trying to play PSO online on Dolphin, I have set the DNS IP to the Schthack IP, I have put in the correct Serial Number and Access Key that I have registered on the website for my HL but still no matter what I do I keep getting the Error 102 when I try to connect ...

I keep having the same thing happen to me as well, I am playing on the Dolphin UWP on Xbox Series X, how do I fix it?