Meta Box

Ok, leaving this last comment, even though it shows how dumb I was and how long it took be to find it 🙁

When defining the fields, on a couple of taxonomy custom fields I was doing this:

public function suburb_fields($meta_boxes)
    {
        $meta_boxes = [
            'title'      => 'Suburb Taxonomy Fields',
            'id'         => $this->text_domain . '-sd-suburb-fields',
            'taxonomies' => ['sd-suburb'],
            'fields'     => [
                [
                    'name'       => __('City', $this->text_domain),
                    'id'         => $this->prefix . 'city',
                    'type'       => 'taxonomy',
                    'taxonomy'   => ['sd-city'],
                    'field_type' => 'select_advanced',
                    'add_new'        => false,
                    'remove_default' => false,
                ],
            ]
        ];

        return $meta_boxes;
    }

Instead of this:

public function suburb_fields($meta_boxes)
    {
        $meta_boxes[] = [
            'title'      => 'Suburb Taxonomy Fields',
            'id'         => $this->text_domain . '-sd-suburb-fields',
            'taxonomies' => ['sd-suburb'],
            'fields'     => [
                [
                    'name'       => __('City', $this->text_domain),
                    'id'         => $this->prefix . 'city',
                    'type'       => 'taxonomy',
                    'taxonomy'   => ['sd-city'],
                    'field_type' => 'select_advanced',
                    'add_new'        => false,
                    'remove_default' => false,
                ],
            ]
        ];

        return $meta_boxes;
    }

Note the $meta_boxes = ... instead of $meta_boxes[] = ...
This stupid mistake on two taxonomy definitions was breaking everything, settings screens, custom post fields and of course taxonomy fields.

Thanks Peter. I have been suspecting load order as the cause but can't see how to fix it...

Hi, I managed to fix this and thought I'd put the answer here for anyone else that comes across it.

Short answer is found on this page https://github.com/composer/composer/issues/11913

Seems that something with the a curl version installed on my Mac. Updating curl fixed it. Doesn't seem to have been the fix for everyone.

In particular this problem only happened when trying to download and install the premium extensions.

Thanks for your reply Peter.

The key definitely is fine as I have it working on multiple sites. But to make sure I generated a new one and tried that and got the same error.