Fatal error: Uncaught Error: Class 'Allegiant_Notify_System' not found

I am receiving the following error on my website:
Fatal error: Uncaught Error: Class 'Allegiant_Notify_System' not found in …/wp-content/themes/activello/inc/welcome-screen/sections/actions-required.php:91
The debug info is:

WordPress Version: 5.4.1
Current WordPress Theme: Activello version 1.4.1
Theme Author: Colorlib - http://colorlib.com
Theme URI: https://colorlib.com/wp/themes/activello/
PHP Version: 7.3.1
MySQL Version: 5.6.39-83.1-log
Apache Version: This information is not available.
Active Plugins:
Akismet Anti-Spam (4.1.5)
Debug Info (1.3.8)
Free Downloads WooCommerce (3.1.8)
Widget Importer & Exporter (1.5.5)
WooCommerce (4.0.1)
WordPress Importer (0.7)

Could I fix this error somehow?

Hi There,

Thanks for reaching out to us.

I’d love to have a look at it and try to help.

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Hope to hear from you soon.