Can't access IP address to reset router

In February of 2019 I purchased a gl-mt30n-v2 router. I connected it to the guest WiFi at my mom’s nursing home and connected security cameras. It has worked fine until 6 days ago. I was going to restart the router. I tried to access the IP I kept getting the message that it could not be found. Is there an alternate IP address? I really need to restart the router so I can get the cameras restarted. Because of covid 19 the cameras are the only way to see my mom. Please help!

Maybe you can follow this guide first:

Can you check if you connected to the router and got a Valid IP address?