Looks like quite a few people (myself included) are now unable to play FF14 on the PS4. The client was patched yesterday morning, and since then has failed to start every time. The error message is CE-30022-7. So far, the only potential fix seems to be to uninstall the whole program, and then reinstall it. With the amount of data you need to download in installation files and updates, those with ISP download limits may have problems with this method.
They are taking the servers down for emergency maintenance tomorrow morning, but haven’t said if that’s to try to fix this issue. As it appears to be a client-side fault, not sure doing anything to the servers would matter anyway.