IP fragmentation is not supported by PS4 or router?

I have a problem with my internet. I have a 50k line and it works fine on my cell phone but not on my ps4.
There's only the sentence, The router used may not support ip fragmentation and some functions are therefore restricted on the ps4 ".

how can i fix this?

Then your PS4 has some problem that I can't describe because I do not have a PS4. But fundamentally, a router must have IP fragmentation because it is a basic function for data traffic.