Error loading API

Hello,

I have a problem that appeared on my site lately. The calendar doesn’t load, I get a message

Uh oh. We ran into a problem: Error loading API

. In the console I see a following error GET (...)/wp-json/ssa/v1/getApi.php 404

My WP is up to date, your plugin is at version 1.5.8.3, running an Nginx server.

The Support tab of the plugin is all green checks, however the debug log shows this:

The following is logged from update_debug_mode()
in (...)/wp-content/plugins/simply-schedule-appointments/includes/class-developer-settings.php line 158:

... apply_filters()
in (...)/wp-includes/class-wp-hook.php line 307:

...... do_action()
in (...)/wp-includes/class-wp-hook.php line 331:
[2022-10-10 13:53:00] $config_transformer

Interestingly, I have a development version of the site with the same setup (hidden behind a VPN) where the problem doesn’t exist.

The page I need help with: [log in to see the link]