Bustacap: workaround until they fix it:  
 - log in to PSN (store.playstation.com) through your browser  
 - after the login open this link: 
https://ca.account.sony.com/api/v1/ssocookie  Copy content of "npsso"  
 - open windows explorer and enter the following into the address bar at the top and press enter 
 %LocalAppData%\GOG.com\Galaxy\plugins\installed\  
 - open the psn_{random number} folder and edit the plugin.py file with your favourite text editor  
 - go to line 64 and change it from: 
 stored_npsso = stored_credentials.get("npsso") if stored_credentials else None  
 to: 
 stored_npsso = "Copied value of npsso" 
 ("copied value of npsso" should be a 64 character long text consisting of numbers, lower case letters and upper case letters) 
 (the quotation marks " " are important!)  
 - restart GOG Galaxy 
 - try connecting with PSN again