Why does it say "card cannot be accessed"when my camera's on?

It probbably means there is something wrong with The sd port

Hi, if you do not have any important data on you SD card, you can format your SD card to fix the problem. Here are two ways to format the SD card:

Format memory card with Windows File Explorer

Step1: Attach the memory card to your computer/laptop and press WIN logo key + E to go to Windows File Explorer.

Step2: Select “This PC” option from the left side panel and then search for your card from the right pane by seeing the label and drive letter of your card.

Step3: Now, right click on your memory card and select “Format” option.

Format with Disk Management

Step1: Connect your camera’s memory card to your laptop/computer.

Step2: Launch Windows Disk Management and look for your card from the volume list, then right-click on your card to open a context menu.

Step3: Select the option to “Format..” and then follow the steps as directed to complete the process of formatting.

While if you have data om the card, remember to make backup in advance.