When the Support Ticket Mail Import Log displays the error "fread() expects parameter 2 to be integer".
fread() expects parameter 2 to be integer, float given error being caused by after-market modules, specifically those which bundle their own version of the guzzlehttp library.
You can recursively search the /modules directory for guzzlehttp to locate any such modules.
The affected modules:
Sectigo WHMCS: modules/addons/sectigo/lib/guzzlehttp/psr7/src/Stream.php line 231
Find
fread($this->stream, $length);
Update
fread($this->stream, (int)$length);