Try the solutions from here: https://askubuntu.com/questions/774458/installed-lubuntu-16-04-version-no-audio-now It's a different Ubuntu version but it might work.
– LogixApr 12 '18 at 17:53
I tried that, it didn't work. I got no protocol specified after I ran sudo gksu pavucontrol
– DekoyApr 12 '18 at 18:20
Please [edit] your question to add the laptop/PC model or even better, the sound card model.
– fosslinuxApr 12 '18 at 22:37
no protocol specifiedafter I ransudo gksu pavucontrol– Dekoy Apr 12 '18 at 18:20