Originally Posted by isaac
Is your forum running on FreeBSD?
On FreeBSD, this library is NOT included automatically. It must be manually installed. This can be done with the following command:
Code
pkg install php70-ctype

source:
https://www.php.net/manual/en/ctype.installation.php

further reading here:
https://www.php.net/manual/en/intro.ctype.php
and here:
https://www.php.net/manual/en/book.ctype.php

in your forum's PHP Info page, you should see under ther ctype section,
Code
ctype functions 	enabled

Our hosting provider uses Debian. Curiously, outbound emails were not impacted by this change until PHP was upgraded. There's another wrinkle in this somewhere. Inliners has been live with UBBT 7.7.5 since 21-Feb using the old PHP version. Switched to PHP 7.4 today and boom.