It's probably using a different address. Look in your router DHCP leases for a new IP that it's using perhaps.
Also in your router configuration, assign the S9s MAC address a static reservation so this never happens again.
Discussion
Hmm did all that with no luck. Weird yeah same IP, was even able to successfully ping it. Weird thing is when I first plugged in got like 2TH/s hash rate in the pool and was online, then dropped to zero.
Trying to reach the IP either says can’t connect, or taking too long to respond.
Maybe will restart the router and S9 and try again later. Thank you for your wisdom!