Since you already checked for drivers and the apps that control sound, HP needs to tell you 1) if it is ready for 10 and 2) how to fix it.
I have an HP 200-5020 PC all in one. Had windows 7...worked great..did the upgrade to windows 10...now I only have sound if I use my earphones..the internal speakers not giving out sound. I checked the drivers as I saw people saying to do and how to ck..I did troubleshoot also. No trouble detected..says drivers are up to date. I am new with PC so can not do a lot of technical things...can anyone help or should I revert back to Windows 7. AND, if I do revert back will that cause any issues? I just did the upgrade Friday and I know you have 30 days to go back. Any hep would be greatly appreciated.