Flash drive is not found or recongized

If your computers will not recognize the flash drive, no data recovery software is going to work (so don't waste your money). Because you were able to confirm this on more than one computer, then the odds are that the problem is within the flash drive itself. What commonly happens to USB drives is that the connector/connections to the small board inside the drive may be broken. This can be caused by any kind of impact to the drive, sometimes we don't even notice it. If that's the case, it should be straightforward to repair.

Otherwise, it could also be an issue with the controller IC or actual NAND memory. In that situation, it may require "chip-off" data recovery which is more involved (and hence more expensive). Ideally, you will want to reach out to a data recovery specialist to get an evaluation done. Most work on a no data/no fee basis but in the end, only you can decide how much the data is worth to you.