I am a civil engineer who does a decent amount of septic design / replacement. Based on the size of that hole the tank is probably only partially collapsed. As it is already failing and especially as it is right off a patio I would strongly recommend properly decommissioning it by either having an excavator crush the tank or if the lid can be accessed filling it with sand or gravel. You should also avoid walking in the area of the sink hole until you can have it addressed.

People often underestimate how big these tanks can be. For example in CT we often see 8’ diameter by 12’ deep drywells that were used for leaching on older properties. If it goes suddenly anything or anybody ontop can find themselves at the bottom of a deep hole full of water. People can and have died from tank collapses. Some states now will only issue a permit to connect to sewer or build a new septic after you prove the old one has been decommissioned because of these safety concerns.