sorry, not been around for a while.
hmm, trying DFU mode is the first thing to try...
can you confirm when you go into DFU mode the led remains off - if not, then I dont think its going into dfu mode (hence why computer still cant see it)
warning it can be a bit fiddly to do this, as you need to hold s1 whilst powering down, and its a tiny button.
also make sure you disconnect everything else from axoloti e.g. usb devices, gpio, and plug the axoloti directly into your computer.
also can you confirm have these axolotis ever worked? or is this a new problem?
(if it never worked, is it a new axoloti, or come from someone else?)