Gmc bose stereo say locked..how do I unlock it

Hello, i have a bose system in a nissian maxima, some reason, my wife was loading cds, holds 6, dont know what she did now it says cd error, had to take it out and take to dealer . cd player would not play, these stereos has a tendacy, to lock up, dont know what dealer did, but they fixed it or changed mine, working now, you might take hot battery cable loose, and count to 7 to clear comp, put back on and see if it works, if you have a remote with it it may be bad