One possibility is that the carrier board itself failed, and this isn’t uncommon relative to number of failures (I have no figures, but I get the idea over the forums that the carrier board fails more often than the module). If you can afford to do it, then you might get a second carrier board and see if you can use that…then you’d know if the module itself is bad or not.
Unfortunately, the developer carrier board is not available separately. Any carrier board could be used to clone the content of the module, but third party carrier boards probably need flash to get the module to actually boot correctly (the board support package will have a different device tree for different carrier boards, but recovery mode for flashing or cloning will not depend on this).
I do not know of anyone who actually repairs these. Schematics are available for the development kit carrier board, and so the simplest failures of power regulators could show a specific component in need of replacement. If you are good at surface mount rework, then this might be ok (and if you have no experience with this, then success is unlikely…you could obtain the right parts and get someone who does rework to make the change). See: