Some SanDisk Extreme PRO CFexpress card readers (SDDR-F451), bundled with the EOS C500 Mark II cameras, may not seat the CFexpress card properly within the card reader preventing it from being detected. For more information please review the announcement from SanDisk.
If the SanDisk Extreme PRO CFexpress card reader is experiencing this issue please contact SanDisk Customer Support. SanDisk has informed Canon that SanDisk will evaluate the reader and, if necessary, offer a replacement.
Sandisk Extreme PRO CFexpress card reader SKUs that may be affected: