FacebookBusiness extension was installed without problems a few days ago but no I have tried adding a different colour to my configurable product and keep getting this error

Notice: Array to string conversion in /var/www/html/app/code/Facebook/BusinessExtension/Model/Feed/ProductFeed.php on line 107

            'main_image' => $this->_fbeHelper->getBaseUrlMedia() . 'catalog/product' . $mainImage,

this is a longer snippet

private function getProductImages(Product $product)
{
    $mainImage = $product->getImage();
    $additionalImages = [];

    foreach ($product->getMediaGalleryImages() as $img) {
        if ($img['file'] === $mainImage) continue;
    }
    return [
        'main_image' => $this->_fbeHelper->getBaseUrlMedia() . 'catalog/product' . $mainImage,
        'additional_images' => array_slice($additionalImages, 0, 10)
    ];
}

Magento 2.3.6

FacebookBusiness extension was installed without problems a few days ago but no I have tried adding a different colour to my configurable product and keep getting this error.

Notice: Array to string conversion in /var/www/html/app/code/Facebook/BusinessExtension/Model/Feed/ProductFeed.php on line 107

            'main_image' => $this->_fbeHelper->getBaseUrlMedia() . 'catalog/product' . $mainImage,

this is a longer snippet

private function getProductImages(Product $product)
{
    $mainImage = $product->getImage();
    $additionalImages = [];

    foreach ($product->getMediaGalleryImages() as $img) {
        if ($img['file'] === $mainImage) continue;
    }
    return [
        'main_image' => $this->_fbeHelper->getBaseUrlMedia() . 'catalog/product' . $mainImage,
        'additional_images' => array_slice($additionalImages, 0, 10)
    ];
}

Magento 2.3.6