Hi [NAME], I would suggest you reseat the expansion cards, the riser cards, and any cables running to either. Then try powering the server back up. If the error persists, please remove anything in slot 3 and then power on the server to see if it clears.   Also, please update the BIOS and iDRAC at your earliest convenience.
I have dell r640 with single cpu configuration (xeon gold 6212U). I am currently using a network daughter card from Intel (68M95). can I add 1 more network card with a single cpu configuration? if possible what riser should i use?
[Dell R640] Two network card with single cpu configuration