My ISO and auto flash in viewfinder?

Ok I'm just starting to learn my teacher online course said for night photos without using flash set camera to ISO 100 f 22 when I do this my camera won't take photos at all my auto ISO keeps flashing in viewfinder even tho I have it set on M I have looked in the menu and can't seem to find this information so I'm asking you if you I have a Nikon D3100 if you have a D3100 or similar please advice me on what I'm doing wrong I need to know if my M is not working so I can put in for repairs while under warranty and for the life of me I just can't find any other setting to stop this I only have kit lens at the moment 18 55 mm is this lens good enough something with the camera or the setting is there a better lens I could buy for this camera for night photos without the flash takes wonderful photos other wise

Added (1). I'm sorry I think this has been a little misunderstood I do have my camera set on M but the viewfinder is still telling me information flashing ISO auto but its defendant set in M its like its not recognizing that I have set it in M but you guys are right I'm not using a tripod I don't have one yet but am going to make an investment in the next day or so but I just really wanted to try out night photography to see if it was what I want to do I'm also quiet interested in landscapes

Taking night photos at f/22 and with the ISO set to 100 will require a tripod for sure

Your camera is telling you that there's NOT enough light to shoot hand held and the flashing ISO is telling you to increase the ISO.

Never use auto ISO if you want to learn how to control your cameras exposure balancing the shutter speed, lens aperture and ISO.

You need to discuss this problem with your instructor and get a better idea of how to set up your camera to shoot such shots.

This is one reason that attempting to learn the fundamentals of photography outside a traditional classroom can be frustrating. You can't had your camera to your instructor so they can look at your camera and make sure that your camera is set correctly for the assignment. For instance, did your instructor have you set the white balance to match the lighting in your night shot? Incandescent is usually the best in most cases unless most of the light is being supplied by fluorescent light

Your teacher is wrong. You do not need f/22 to shoot night photos without a tripod. Unless you're trying to achieve maximum depth-of-field with a scene that has a foreground almost right in the front of the lens and mountains far in the distance, then f/11 will work just perfectly fine. A possible reason why your camera isn't taking the shot is because the f/stop is too large, resulting in an exposure time that's over 30 seconds (the limit of most DSLRs without using bulb).

Don't use auto ISO, set the ISO manually. This should be really easy to find in your manual (just search up ISO in the index of the manual). You also do not need to use "manual" mode for good photos. M mode is great for static subjects and when you have a lot of time; for day to day use, I prefer using A (aperture priority) mode.

Another tip for taking night shots, is of course, to use a tripod. Don't wait until the sky is totally pitch black either, you'll want a little bit of the 'blue' left in the night sky for better results.