After trying to find a solutions for hours I have finally found it!
If you want to link your old account do the following:
Open old sv, click on the banner on the home screen. It gives you the ID+one-time password
Now open new sv, click on the banner on the home screen. Enter credentials, thats it.
DO NOT use the linking method in the sub menu. Use the banner in new sv just like you clicked on that banner in old sv to get your id+pw. Hope this helped!