Lock won't open

SOURCE: Master Lock 5400D (Please help!)

Try lubricating with a silicone spray oil, And work the cover to try and free it.

If this has no effect, I suggest you visit a locksmith, that should be able to identify the fault.
If it is unable to be easily reached/ rectified, you may need to remove the cover entirely, or purchase a replacement lock.

Hope this helps.

SOURCE: Master lock 5400D lock box

Master lock offer a free replacement service for locks which develop a mechanical defect during normal use.
See their website here for further information -

http://www.masterlock.com/customerservice/

If the lock has been forced or tampered with to cause this problem, then a replacement is needed.

Hope this helps

SOURCE: how do you open a

It would appear that you made a mistake in setting your new combination on your Master Lock 5400d and did not register the combination at Masterlockvault.com. The only way to open your lock is by using the correct combination. There is no other way. Most mistakes are normally one or two digits out, so you may wish to try variations on what you thought you set.

Apart from that you can either try every possible combination or you will need to contact the manufacturer. But they cannot assist you if the lock does not have a serial number (they recently stopped applying serial numbers for greater security) and they will not assist if the lock is already secured to anything. There are a number of other hurdles as well, click here for details. Given that they state that you will have to wait four to six weeks for an answer, it's going to be far quicker to just try every possible combination.