Problem

Access in API Manager performed via Nginx having the "Feature-Policy" header set with directive "synch-xhr none" fails in Firefox.
Nginx configuration file extract:

add_header Feature-Policy *geolocation none;notifications none;push none;sync-xhr none;

Resolution

This is caused by the fact that "synch-xhr none" is not supported in Firefox: https://developer.mozilla.org/en-US/docs/Web/HTTP/...

Removed in the Nginx configuration file "sync-xhr none" part and restart Nginx to take into account the modification.