I realize the alternator is new and the battery is newer, but what you described sounds like we don't have the power needed to make things work properly.
So, I need you to do me a favor. First, make sure the battery terminals are both clean and tight. Next, I need you to check the alternator output when the vehicle is running. Here is a link that explains how it's done. You will need a multimeter or voltmeter.
If the alternator passes the test, remove the battery and have it load tested. Most parts stores will do it for you free of charge.
Let me know the results.
Take care and Happy New Year.
Saturday, December 31st, 2022 AT 6:33 PM