The screen remains black after modification

• Processor (CPU): AMD 3700X
• Main Memory (RAM): 2 x 16 GB Crucial Ballistix (there is only 1 bar currently installed for troubleshooting)
• Motherboard: Asus TUF B550M
• Power Supply: Enermax Platimax 500W
• Graphics Card: GTX 1070

2. Describe your problem. The more accurately and better you describe your problem, the better it will be to help you (additional pictures may be useful, for example):

The computer (motherboard and CPU) was transformed and a water cooling system was installed. After putting everything back together, the screen will stay black.

3. What steps did you take / actually tried to solve the problem and what came out?

Zero method implemented: everything except the motherboard and CPU -> beep code
Added RAM -> Different beep code
Graphics card for this -> Beepcode remains the same

According to the zero method, the graphics card is defective, annoying, but it is likely that it will be slightly damaged when rebuilding the cooler. The card was expanded and tested by a friend at the computer. Here the computer starts up without any problems and displays a live image, so not the graphics card after all?
Phonetic Code: 1x long, 3x short, according to Asus (https://www.asus.com/de/support/FAQ/1029959/) either problems with the graphics card (and its power supply) or problems with the CPU cooling (but I have a fan connected to CPU_FAN). The power supply should already be sufficient and have been previously used with the same card, 8Pin connected (many times turned on and not connected).

CMOS clearly brought no improvement.

Now I’m really confused, the best way to go. My hardware exchange options are somewhat limited now. I thought about whether the PCIe slot is defective, but it is not noticeable either on the motherboard or on the graphics card contacts.

Maybe someone still has a good idea, thank you very much.

LG, wool first