@VoodooChild76  Hello, 

Sorry for the late response, may I know did you set up RE650 in the extender mode which is wirelessly connected to main router?

If you have router <wireless> RE650<Ethernet cable> PC/ PS4:

1.  Confirm PC could get internet from the range extender via cable 

2. check if PS4 works, if not, you could  try to  manually set up an IP  & gateway which are in router's IP range with the help for PS4 support. 

3. Double-check the Advanced rules on router that might affect the PS4:  like Blacklist/ Whitelist/ Access control on router

Also check if PS4 could get internet from router.