What does response code 406 signify? (It's not listed in the API reference docs)

[AdamMVF]

I'm trying to setup some API calls in python for updating and creating customers.  The 'GET' calls are working OK for retrieving information however I'm now trying to update a customer's details, which is a 'POST' call, and I'm getting an error response code 406, which is not listed on the API reference doc (https://developer.loyverse.com/docs/#section/Handling-errors)

Can anyone tell me what 406 means so I can troubleshoot the problem?

Thanks 

***UPDATE***  Answer not urgent anymore.  I started from scratch in POSTMAN and constructed a working call.  Still not sure of the exact meaning of error 406, but it was to do with the format of the header and/or payload. 

Edited January 24, 2023 by AdamMVF
updated, answer not required anymore

[Yasuaki]

Hello @AdamMVF

Thank you for your information.
For our information, may I know how you solved error 406?