If you, or several people, suddenly can't access a door you could before
or if you, or several people, suddenly can't access doors you could before, this is your place.
Please include your info and the door to which you cannot access but previously could. If you can include any information about the card reader reaction ("flashed a bunch of colors, did nothing" or "there is no light on the card reader" or "light went green but door didn't unlock") we find these very helpful.
One caveat - if you're a student (any level) and it's January, September, or June, your access probably expired and you need to reach out to your department.