Incompatibility or what?

With the working GPU installed, check in your UEFI and disable CSM (under Advanced > ACPI) save and shut down then try the GPU again. If that doesn't work then you can try updating the GPU's vBIOS, see if the card has a newer vBIOS and carefully follow the instructions to flash it if it does. That may fix the issue. Unfortunately some GPUs are simply not compatible with older motherboards.

Ouch, that is a tough one to troubleshoot. Your i5 3350P doesn't have integrated graphics so we can't even test with the onboard display outputs. 5 (long) beeps means the system is not even detecting your GPU. There are a few things you can try if you have not already done so:

Remove the GPU and clean it's contacts with isopropyl alcohol

Clean out the PCIe slot with a (dry) toothbrush or firm paint brush to make sure there is no debris in there preventing the GPU from properly seating.

Reinsert the GPU and carefully check to make sure it is seated all the way into the slot. Sometimes it can feel like it has seated properly but it is in fact not all the way in.

If nothing I listed above works then take the motherboard out and assemble the system outside of the case. This will allow you to check if the GPU is seated properly by looking at the slot area. In some PC cases the slots at the back of the case are too high and prevent PCIe cards from properly seating.

If after all that you still can't get the system to post then remove the CPU and check for bent pins. If there are bent pins or the CPU is not properly lined up it can cause issues with your PCIe lanes. Make sure there is no debris in the socket and nothing smeared on the underside of the CPU, conductive thermal paste can easily cause the issues you described.

If none of my advice helps then your only other option is to try and find an older GPU to test on the board, something like an old Geforce 210 or equivalent that is guaranteed to work with your board.

Good luck and let us know how it goes.

Edited by Xaltar - 10 Apr 2019 at 4:28pm

[QUOTE=Slick_vic] I have a motherboard H61m/dg3/usb3 and a video card Sapphire Radeon R9 280X Toxic 3GB GDDR5 384-bit and not work. It give me 5 beep`s. The BIOS version is the last 1.3. I try all the way`s and I can`t start the video card. Any idea`s why? The power source it`s 835W power.Modular PC Source 835W RAIDMAX THUNDER V2 80+Bronze