I've had this problem for a month now, and I can't ever connect to PSN related networks anymore using my internet. I've contacted sony support chat for this, and they told me that it was my ISP's issue, and told me to open up some ports.
After that, I contacted my ISP and they told me it would cost $70 as a "service fee" to open up the ports, so I opened them up myself but the issues were still not fixed. The errors sets in, and lasts around several days, until something magically happens and lets me use PSN for a short period of time before the error sets in again. I'm switching to a new ISP next week to solve this problem and to lower my monthly bill costs.
I hope that this issue isn't as severe as it is for you, but here are a few suggestions that I'd recommend to you before contacting sony support and telling them your side of the story.
Restart your router/modem
Check if the problem persists on another WiFi network (try connecting to a different WiFi when you visit a cafe or something or try using your phone's data network hotspot)
Check if the internet browser still works.
Change your wifi's DNS settings to google's in the network settings -> wifi network -> advanced (8.8.8.8 and 8.8.4.4)
Tell me how these steps went. If your vita connects to PSN without 2304-9, it should be your internet's issue.