It sounds like the battery is weak and the alternator (although it's new) isn't producing. That can be caused by one of two fuses. If you take a look at pic 1, I highlighted two fuses. One is a simple fuse and the other is a fusible link and located at the positive battery terminal. I need you to check both.
In addition to simply checking the fuse, make sure power is to it and from it. Here is a link you may find helpful:
If you look at pic 2 and 3, it shows the locations of the fuses.
Let me know what you find or if you have other questions.
Images (Click to enlarge)
Sunday, December 20th, 2020 AT 10:36 PM