My bike is locked to an indoor bike rack with a folding ABUS keyed bike lock. Today I couldn't turn the key to release the lock after work. No problem locking it in the morning. Tried wiggling, banging, twisting and pulling on "link". Any suggestions?
Lock have typically two kinds of problems. How far can you push the key in? Does it go in only partly, or does it go in fully but then you can't turn it? Often the disks inside have rotated so that you can't get the key in completely. Then it helps if you take a stiff wire or thin screwdriver and wiggle it up and down in the keyhole, and then try again with the key. But if the key goes in but doesn't turn, then it might be clogged up with dirt, in this case degreaser might help. Make sure you dry the lock carefully afterwards and don't use oil or grease to lubricate, they will just attract dirt and clog it up again. If you want to lubricate, use dry lubricant like graphite.
You could try spraying some WD-40 in there. And then reach for a hammer.
Also check if your key isn't damaged.