You will need a SD card reader like below in order to execute SD Card Recovery Process.
https://www.amazon.com/dp/B01BXSKPES/ref=cm_sw_em_r_mt_dp_WWYGM6018P836Y2SJ4SP
https://www.amazon.com/dp/B06Y1G18KS/ref=cm_sw_em_r_mt_dp_G3MCQCPVKT5X7BRQXJPB?_encoding=UTF8&psc=1
Please find step by step instruction to recover SD card of your Flex below.
- Download and install Etcher from https://www.balena.io/etcher/
- Download Flex image from https://api.miops.com/utils/flex_firmware_v63.img.zip
- Unzip Flex image file. Uncompressed file name: fiex_firmware_v63.img
- Start Etcher
- Click “Flash From File”
- Select flex_firmware_v63.img from file browser
- Insert your SD Card to your SD Card writer and click “Select Target”
- Select your SD Card from list and click to “Select(1)”
- Click to “Flash!”
- Wait for finish. After completed you can insert SD Card to Flex and power up your device.