I may or may not be able to help you. Would you please tell me what the make & model is?
Royal 500dx electronic
I'm sorry to report that my expertise doesn't include the Royal line.
What I can tell you, look in your manual for the corrective measure called "Initial Reset". I am a Sam4 Dealer and we use this feature to unlock almost any lockup that occurs during the operation.
You might also call the MFG. as there always is a "Master" password ***** or they would not allow it to be password ***** Afterall it is not an "Iphone"....
Good luck, I wish I could help further.