I have a red circle on the top of the screen. And the Fuze+ is only playing out of one side of the headphones.
I would try the manual firmware update method, and see if reinstalling the firmware fixes anything. If that doesn’t help, contact Sandisk, and see if your player can be exchanged (assuming the warranty is still valid).
Red circle on screen - I believe this is an indication that subscribed content has expired, like audible books downloaded from the library or Rhapsody music services.
Headphone issue - Could be a bad wire in your headphones, but it they play fine with another device, you might check to make sure they are plugged in all the way. Twisting while pushing helps. If this is a new player, be aware that the jacks are very tight when new, so sometimes you have to give the plug an extra little oomph when inserting it. The jack will loosen up with use.
It’s doubtful re-applying the firmware will help with this matter. If you’ve had this player for a while and it just started doing this and you’ve eliminated the headphones as the problem, you should contact SanDisk Tech Support/Customer Service about a possible warranty replacement, provided of course it is still within the warranty period (US - 1year, EU - 2 years).