PS4 Player Can't Join Realm: "Unable to join specific server"

I have recently created a realm and am on my free trial after the new crossplay update. I replaced the realm world with a survival world I already had and invited my friend on PS4 from my PC running Windows 10 edition. Immediately, my friend is met with the error: "Unable to join specific server." I tried removing him and inviting him numerous times and also tried inviting from my Xbox One to no avail. I also invited someone on Windows 10 edition and they could join no problem.

Any help would be greatly appreciated. 

Thanks!