hi, just purchased but i get this error

[21-Sep-2021 12:33:32 UTC] [FATAL] Exit error: Uncaught Error: Class 'Phpfastcache\Helper\Psr16Adapter' not found in /home/ozdesi54/public_html/xxxxxxxx/wp-content/plugins/instamatic-instagram-post-generator/instamatic-instagram-post-generator.php:2041 Stack trace: #0 /home/ozdesi54/public_html/xxxxx/wp-content/plugins/instamatic-instagram-post-generator/instamatic-instagram-post-generator.php(1024): instamatic_run_rule('0', 0) #1 /home/ozdesi54/public_html/xxxxxx/wp-includes/class-wp-hook.php(303): instamatic_run_my_action_callback('') #2 /home/ozdesi54/public_html/xxxxxxx/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters('', Array) #3 /home/ozdesi54/public_html/xxxxxxx/wp-includes/plugin.php(470): WP_Hook->do_action(Array) #4 /home/ozdesi54/public_html/xxxxx/wp-admin/admin-ajax.php(187): do_action('wp_ajax_instama...') #5 {main} thrown, file: /home/ozdesi54/public_html/xxxxxxx/wp-content/plugins/instamatic-instagram-post-generator/instamatic-instagram-post-generator.php, line: 2041 - rule ID: 0!