Which memory card are you using?
Have you tried another card?
Are you inserting it properly....they definitely can be fiddly to insert?
He can't format it in the AC if the AC won't even acknowledge the card is installed.It's surprising that any modern SD card from a major manufacturer would not come already formatted. You don't list what card you have though.
While you can format it in the computer, it's probably a better bet (just this first time to be sure it's not a bad card) to format it in the aircraft, using the format option in DJI Go 4.
For the computer, in the M2P owners manual, in the Specifications section under Supported File System, it lists FAT32 for 32GB or less, or exFAT for larger cards.
Chris
He can't format it in the AC if the AC won't even acknowledge the card is installed.