Hi and welcome to JustAnswer,
Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, how many speakers are connected please? And have you re-checked the speaker wiring?
Going through the basics, have you considered/tried a RESET?This is very critical - a reset however would not be corrective of an internal hardware concern; but it would be confirmed. In some instances, it may even expose other issues.
If so, are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter and even a soldering iron?
Additionally, would you be able to make use of the schematic diagrams?