Someone on quora asked:
There are many people using PLDT that are able to play online using the PS4. There is probably some sort of configuration or routing issue in your area which is causing the problem.
Also, try a hard reset on your router every so often. I had this issue with my Bayantel router that my PS4 suddenly can’t connect to PSN for a few days. After some time and a few router restarts, it got better.
I suggest calling Sony support. Tell them about the error and ask them for technical details of the possible cause, and if there are any diagnostics you can do. Ask them what you need to tell your ISP to check