SD cards FAT16, FAT32 & exFAT

SanDisk SD cards come prefomatted as FAT16, FAT32 & exFAT according to size

• 2GB FAT16
• 4GB to 32GB FAT32
• 64GB or higher exFAT

https://kb.sandisk.com/app/answers/detail/a_id/312/related/1

If you have a SanDisk Wireless Flash Drive or SanDisk Wireless Stick

• 16GB & 32GB SD cards must be formatted as FAT32
• 64GB and higher capacity drives are compatible and can be formatted as exFAT

https://kb.sandisk.com/app/answers/detail/a_id/17546/~/wireless-stick-exfat-support

If you are still having problems try reformatting them with EaseUs Partition Manager

• https://www.easeus.com/partition-manager/epm-free.html

or windows disk manager

• https://kb.sandisk.com/app/answers/detail/a_id/107

if none of the above work you can get a replacement SanDisk Wireless Flash Drive or  SanDisk Wireless Stick from SanDisk

• https://kb.sandisk.com/app/rmaform