FAIL_SIG error from some methods

[hicreate]

Integration built using the wrapper works as expected in localhost (PHP 7.3, MAMP Pro) built as a wordpress plugin.

When ported to production server I get FAIL_SIG on some methods, despite not amending the channel_id.

I can get response from show_channel and to check rate limit but get error on list_tours and list_tour_images

No details beyond 'FAIL_SIG' in the dashboard log or docs to help identify the cause.