Reconnect your AMD GPU card back on to the Motherboard and power up.
Your RX7900GRE requires Additional Power Connector2x8-Pin from the PSU to your GPU Card power connections.
Make sure you have 2 different PCIe x 8 pin GPU power cables and not one cable with 2 PCIe x 8 Pin connectors.
Some PSUs have problems with one PSU PCIe power cable with 2 PCIe Power connectors to a GPU card ("Y" type cable connection).
IF the same thing occurs look at your Motherboard's EZ DEBUG LED Lites and see which LED is lit up. That will tell you which hardware is not passing the BIOS test when booting up:
Since everything work fine with your APU IGPU without the GPU card most likely the EZ DEBUG LED for the GPU will be lit. If something different please post back.
You do have all of your Motherboard's Drivers updated including BIOS, AMD CHIPSET, and GPU correct?
Go here to download and update all of your Motherboard's Drivers except the AMD CHIPSET and GPU driver: https://www.msi.com/Motherboard/PRO-B650M-A-WIFI/support#driver
Here is the latest AMD CHIPSET for the B650 from AMD Download page: https://www.amd.com/en/support/downloads/drivers.html/chipsets/am5/b650.html
Or better yet install your Motherboard's GPU driver first and see if it boots up normally from here: https://www.msi.com/Motherboard/PRO-B650M-A-WIFI/support#driver
Here is the latest AMD GPU driver for your RX 7900GRE: https://www.amd.com/en/support/downloads/drivers.html/graphics/radeon-rx/radeon-rx-7000-series/amd-r...
The latest AMD GPU driver 24.7.1 seems to be causing many issues with Users so I advice you first install a older version first and see what happens from here: https://www.amd.com/en/support/downloads/previous-drivers.html/graphics/radeon-rx/radeon-rx-7000-ser...
NOTE: If you still are having issue after doing everything above then the best thing to do to verify your GPU Card is not defective is by installing the GPU card in another compatible PC or have it tested at a computer shop or you can install a different GPU card and see if it boots up or not.