Resetting your factory settings will not erase your music & audio books. It will only reset the personal preferences you have changed (screen time, brightness, etc.). “Formatting” is what will erase all user-added content.
It has been long known that the Clip Sport+ has problems with certain bluetooth phones/speakers. There are some it just will not connect to. If yours connect with a wireless speaker but not your earbuds, these may be ones that it has a problem with. The only solution is to A.) make sure you have the latest firmware, or B.) try different ones.
