Front end errors

I am getting the following errors on the front end. I have already uploaded via FTP the latest version of the theme files (manually removing all the old fields from the previous version) and I am using PHP 7.3.27

Fatal error: Uncaught Error: Call to undefined function avia_get_option() in /home/customer/www/milkasprofessional.com/public_html/wp-content/themes/enfold/header.php:6 Stack trace: #0 /home/customer/www/milkasprofessional.com/public_html/wp-includes/template.php(730): require_once() #1 /home/customer/www/milkasprofessional.com/public_html/wp-includes/template.php(676): load_template(‘/home/customer/…’, true, Array) #2 /home/customer/www/milkasprofessional.com/public_html/wp-includes/general-template.php(48): locate_template(Array, true, true, Array) #3 /home/customer/www/milkasprofessional.com/public_html/wp-content/themes/enfold/index.php(10): get_header() #4 /home/customer/www/milkasprofessional.com/public_html/wp-includes/template-loader.php(106): include(‘/home/customer/…’) #5 /home/customer/www/milkasprofessional.com/public_html/wp-blog-header.php(19): require_once(‘/home/customer/…’) #6 /home/customer/www/milkasprofessional.com/public_html/index.php(17): require(‘/home/customer/…’) #7 {main} thrown in /home/customer/www/milkasprofessional.com/public_html/wp-content/themes/enfold/header.php on line 6