No SD Card

I have 2 SanDisk Ultra Plus64gb cards. I have filmed on both of them with no problem. Now when I go to use them it says no SD card on the camera and it won't let me record. This has happened before with a different card. ( I used one that was on the approved list) It's as if after recording an hour the card is no good. Is there any way to fix this? Am I doing something wrong?

Thanks in advance for helping out a newbie. I'm using this camera to film comedians at a comedy club.

I just had the same problem. Not used card for a while and now the camera won't recognise it.
Problem was FAT32 format.
Formatted card as exFAT on my iMac and now it works fine.
HTH
Nigel

Try formatting the card in camera.