Oh, thats a pitty.
What you can try is to boot it with only CPU + 1 stick of RAM (in the second slot counting from the CPU to the right), and yes I will suggest you hook up a monitor, keyboard and even a mouse. If it doesn't work that way, then you try to update the BIOS one more time, but be sure to do exactly what MSI explain below, you don't need anything but motherboard + PSU + a USB flashdrive (I hope thats your particular mobo).
According to MSI website manual for MSI PRO B650-P WIFI (
https://download.msi.com/archive/mnu_exe/mb/PROB650-PWIFI.pdf) the procedure is as follow:
Updating BIOS with Flash BIOS Button
1. Please download the latest BIOS file that matches your motherboard model from
the MSI® website.
2. Rename the BIOS file to MSI.ROM, and save it to the root of the USB storage device.
3. Connect the power supply to CPU_PWR1 and ATX_PWR1. (No need to install CPU
and memory.)
4. Plug the USB storage device that contains the MSI.ROM file into the Flash BIOS
Port on the rear I/O panel.
5. Press the Flash BIOS Button to update BIOS, and the LED starts flashing.
6. The LED will be off when the process is completed.
Did someone in Microcenter told you you need it a BIOS update?, cause far as I know you don't need a BIOS update for that CPU you got to work with that particular motherboard..... well actually to any motherboard.