my flash drive used to work with my macbook but now the laptop cannot recognize

Try another USB port. If you are using a hub or other adapter, then use another adapter or plug the drive directly into the computer.

In Disk Utility click on "View" and select "Show All Devices" to see if the physical flash drive shows up in the left pane of Disk Utility.

If you have another computer try to re-partition and format the flash drive on it, then see if the Mac will see the flash drive. Maybe even try reformatting the flash drive on a Windows PC. I've had issues erasing some flash drives on one version of macOS and reading it on another version of macOS.

I've had issues with some flash drives being properly recognized at times on a Mac. If the flash drive was made into a bootable drive, macOS may not always be able to erase it without first writing zeroes to the drive or reformatting it on another PC. Or perhaps your flash drive is beginning to fail. USB flash drives are not the most reliable devices.

Restart your computer. I had to do this with my Mini since the external drives would cause the USB ports to become deactivated until a restart.