This indicates that a signed token request, sent to Ably to request a token, is not valid: the cryptographic signature isn't what it should.

The most likely explanation for this is that the api key used to instantiate the library that generates the token request is not correct. Double check that you haven't accidentally clipped off the last letter or two, or added a space at the end.

If you've double-checked that and are still getting this error, try to get a debug-level log of the generation of a token request, and contact us for more help.