Errors after activation of plugin

I activated the plugin but when I tried to access the settings I got an error. I couldn’t get into the settings and the site wouldn’t come up in another tab. I deactivated the plugin and the site came back.
I got this a message in email indicating that this plugin created an error and they sent me the info below. This plugin would be perfect if it worked. Perhaps you can tell me what the problem might be.

Error Details
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An error of type E_ERROR was caused in line 434 of the file /home/estatedept/public_html/dev.estatedept.com/wp-content/plugins/wc-markup/admin/class-wc-markup-admin.php. Error message: Uncaught Error: Call to undefined function wm_fs() in /home/estatedept/public_html/dev.estatedept.com/wp-content/plugins/wc-markup/admin/class-wc-markup-admin.php:434
Stack trace:
#0 /home/estatedept/public_html/dev.estatedept.com/wp-includes/class-wp-hook.php(308): Wc_Markup_Admin->wc_markup_section_settings(Array, 'markups')
#1 /home/estatedept/public_html/dev.estatedept.com/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array)
#2 /home/estatedept/public_html/dev.estatedept.com/wp-content/plugins/woocommerce/includes/admin/settings/class-wc-settings-page.php(130): apply_filters('woocommerce_get...', Array, 'markups')
#3 /home/estatedept/public_html/dev.estatedept.com/wp-content/plugins/woocommerce/includes/admin/settings/class-wc-settings-page.php(98): WC_Settings_Page->get_settings_for_section('markups')
#4 /home/estatedept/public_html/dev.estatedept.com/wp-content/plugins/woocommerce/includes/admin/settings/class-wc-settings-page.php(211): WC_Settings_Page->get_settings('markups')
#5 /home/est