Help with Troubleshooting PHP Fatal error

I modified an existing page containing items for sale by adding new items. We use WP Simple Cart. The cart buttons had worked for all items before today’s update and I tried one add to cart (I did this test in sandbox mode) after I had published the page today and everything worked fine.

I noticed that a few fonts needed to be corrected on the page and after cleaning up the page, I republished it. Then in WP Simple Cart live mode, I added to cart an inexpensive item and an error appeared:

PHP Fatal error:  Uncaught TypeError: Unsupported operand types: int + string in /home1/amindame/public_html/wp-content/plugins/wordpress-simple-paypal-shopping-cart/includes/wspsc-cart-functions.php:103
Stack trace:
#0 /home1/amindame/public_html/wp-content/plugins/wordpress-simple-paypal-shopping-cart/wp_shopping_cart.php(57): print_wp_shopping_cart('')
#1 /home1/amindame/public_html/wp-includes/shortcodes.php(356): show_wp_shopping_cart_handler('', '', 'show_wp_shoppin...')
#2 [internal function]: do_shortcode_tag(Array)
#3 /home1/amindame/public_html/wp-includes/shortcodes.php(228): preg_replace_callback('/\\[(\\[?)(show_w...', 'do_shortcode_ta...', '<div class="fl-...')
#4 /home1/amindame/public_html/wp-content/plugins/beaver-builder-lite-version/classes/class-fl-builder.php(1886): do_shortcode('<div class="fl-...')
#5 /home1/amindame/public_html/wp-content/plugins/beaver-builder-lite-version/classes/class-fl-builder.php(1942): FLBuilder::render_content_by_id(3811)
#6 /home1/amindame/public_html/wp-includes/class-wp-hook.php(307): FLBuilder::render_content('\n\n\t<h3>US Membe...')
#7 /home1/amindame/public_html/wp-includes/plugin.php(191): WP_Hook->apply_filters('\n\n\t<h3>US Membe...', Array)
#8 /home1/amindame/public_html/wp-includes/post-template.php(253): apply_filters('the_content', '<!-- wp:fl-buil...')
#9 /home1/amindame/public_html/wp-content/themes/astra/template-parts/content-page.php(54): the_content()
#10 /home1/amindame/public_html/wp-includes/template.php(772): require('/home1/amindame...')
#11 /home1/amindame/public_html/wp-includes/template.php(716): load_template('/home1/amindame...', false, Array)
#12 /home1/amindame/public_html/wp-includes/general-template.php(204): locate_template(Array, true, false, Array)
#13 /home1/amindame/public_html/wp-content/themes/astra/inc/class-astra-loop.php(109): get_template_part('template-parts/...', 'page')
#14 /home1/amindame/public_html/wp-includes/class-wp-hook.php(307): Astra_Loop->template_parts_page('')
#15 /home1/amindame/public_html/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array)
#16 /home1/amindame/public_html/wp-includes/plugin.php(476): WP_Hook->do_action(Array)
#17 /home1/amindame/public_html/wp-content/themes/astra/inc/class-astra-loop.php(197): do_action('astra_page_temp...')
#18 /home1/amindame/public_html/wp-content/themes/astra/inc/class-astra-loop.php(174): Astra_Loop->loop_markup(true)
#19 /home1/amindame/public_html/wp-includes/class-wp-hook.php(307): Astra_Loop->loop_markup_page('')
#20 /home1/amindame/public_html/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array)
#21 /home1/amindame/public_html/wp-includes/plugin.php(476): WP_Hook->do_action(Array)
#22 /home1/amindame/public_html/wp-content/themes/astra/inc/core/theme-hooks.php(267): do_action('astra_content_p...')
#23 /home1/amindame/public_html/wp-content/themes/astra/page.php(32): astra_content_page_loop()
#24 /home1/amindame/public_html/wp-includes/template-loader.php(106): include('/home1/amindame...')
#25 /home1/amindame/public_html/wp-blog-header.php(19): require_once('/home1/amindame...')
#26 /home1/amindame/public_html/index.php(17): require('/home1/amindame...')
#27 {main}
  thrown in /home1/amindame/public_html/wp-content/plugins/wordpress-simple-paypal-shopping-cart/includes/wspsc-cart-functions.php on line 103