WordPress caught an error with one of your plugins, Modern Events Calendar Lite

The site will go down if I activate the plugin now. It worked until I tried to change the color on the theme. Nothing else was changed, all was working normally prior to the color change. Even recovery mode did not work and I had to deactivate the plugin via ftp.

Here is the email:

Since WordPress 5.2 there is a built-in feature that detects when a plugin or theme causes a fatal error on your site, and notifies you with this automated email.

In this case, WordPress caught an error with one of your plugins, Modern Events Calendar Lite.

First, visit your website (https://ruralroadsfrederickmd.org/) and check for any visible issues. Next, visit the page where the error was caught (https://ruralroadsfrederickmd.org/wp-admin/) and check for any visible issues.

Please contact your host for assistance with investigating this issue further.

If your site appears broken and you can’t access your dashboard normally, WordPress now has a special “recovery mode”. This lets you safely login to your dashboard and investigate further.

To keep your site safe, this link will expire in 1 day. Don’t worry about that, though: a new link will be emailed to you if the error occurs again after it expires.

When seeking help with this issue, you may be asked for some of the following information:
WordPress version 5.6.1
Current theme: Arrowtic (version 1.0.3)
Current plugin: Modern Events Calendar Lite (version 5.16.6)
PHP version 7.4.10

Error Details
=============
An error of type E_ERROR was caused in line 23 of the file /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-content/plugins/modern-events-calendar-lite/app/features/mec/dyncss.php. Error message: Uncaught Error: Call to undefined function ctype_xdigit() in /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-content/plugins/modern-events-calendar-lite/app/features/mec/dyncss.php:23
Stack trace:
#0 /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-content/plugins/modern-events-calendar-lite/app/features/mec/dyncss.php(37): mec_dyn_hex2rgb(‘585d3f’)
#1 /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-content/plugins/modern-events-calendar-lite/app/libraries/factory.php(484): include(‘/hermes/bosnacw…’)
#2 /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-includes/class-wp-hook.php(287): MEC_factory->mec_dyncss(”)
#3 /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#4 /hermes/bosnacweb05/bosnacweb05ch/b1532/ipw.johnhanson/wp/wordpress/wp-includes/plugin.php(484): WP_Hook->do_action(Array)
#5 /hermes/bosnacweb05/bosnacweb05ch/b1532/