Thanks for explaining @tescher. It sounds like the issue may be related to the network you're using to connect to Pandora, however, first I would recommend you to try the troubleshooting steps for Firefox:
Firefox Troubleshooting
I've included the links for other browsers below in case you'd like to try them our aswell.
Edge Troubleshooting
Chrome Troubleshooting
Safari Troubleshooting
Now, for the network issues, if possible, please try connecting your computer directly via an Ethernet cable and see if that helps. If there is no change, try rebooting your connection:
Shut down your device completely;
Unplug your modem and router, wait one full minute, and then plug them back in;
Wait five more minutes to allow the modem and router to fully boot back up;
Turn your device back on and try Pandora again.
If Pandora still isn't working, could you check if you're able to connect to your network using another streaming service? You might also try connecting your device to an entirely different network, or using a different device on your current network, to see if your streaming improves. Let me know how it goes.
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