Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
Lets start with a permissions repair first.
Go your applications folder, utilities, and launch disk utility.
Then click your mac HD on the left, and then click repair disk permissions on the lower right.
Then for good measure follow these steps t o make sure your mac is set to play from the internal speakers. https://support.apple.com/en-us/HT203186
If you get stuck or run into any issues, let me know.
If you are satisfied with the solutions / answer I have provided please remember to click and submit a 5 star rating, as that is the only way I am credited for assisting you.Thank you,Dustin S