Hello Rick Learned,
Thanks for using Apple Support Communities, it's great to have you here.
We would recommend that you test this out on a different Wi-Fi network if possible, to try and rule out a potential network issue. If you aren't able to test on a different network, try power cycling your existing network to see if that may help. You may want to consult with your internet service provider, but power cycling generally just requires restarting your modem and router (sometimes those two are the same device). Once you reboot the network, reboot your iMac as well and then test the issue again. Hopefully this does the trick!
If you do purchase a song and it doesn't play as expected, you can always feel free to request a refund by following the steps here: Request a refund for apps or content that you bought from Apple - Apple Support
Thank you for being a part of the community here. We hope this information helps!
Best wishes.