Hi @smartwebcanada
I’m sorry for the delayed reply, for some reason we didn’t get notification about your topic.
Probably the “mbstring” PHP extension installed on your site:
https://www.php.net/manual/en/mbstring.installation.php
Contact your host and ask them to install and enable this PHP extension.
Also, this mb_convert_case() function is only used since 3.5, which is not available for WordPress free yet. This suggest you’re using the Pro version, so please contact us here for support:
https://smartslider3.com/contact-us/support/
Also, we’ll remove this code from the upcoming version, which we plan to release tomorrow. If you contact us at our support channel, I can send the new installer before its released.
As per forum rules, commercial products are not supported in these forums. So we can’t help pro customers here.