Disney Plus requires a minimum internet bandwidth of 5 Mbps to use their platform without issues. Now, if the Disney Plus app is not working on the PS4, your network connection could be running slow, or your current plan is slower than the required speed.
Beside above, does PlayStation 4 have Disney Plus?
Disney+ is supported on PS4 and PS5 models. On PlayStation 4, find the Disney+ app in the PlayStation Store. On PlayStation 5, find the Disney+ app via Media > All Apps.