Server error while processing page link

SYSTEM INFORMATION
OS type and version REQUIRED

| Webmin version | REQUIRED | 1.990

hello there, been trying to figure this out but i havent been able to… so please excuse my ignorance. the issue i have is as shown:

whenever i try to open the link i get this error...  nginx error while reading response header from upstream error 500 server error log: Stack trace:
#0 /var/www/pc/repair/pc.php(12487): printclaimticket()
#1 {main}
  thrown in /var/www/pcrt/repair/pc.php on line 2919" while reading response header from upstream, client: 104.35.178.220, server: _, request: "GET /pc/repair/pc.php?func=printclaimticket&woid=6362 HTTP/1.1", upstream: "fastcgi://unix:/run/php/php-fpm.sock:", host: "mydomain.com", referrer: "https://mydomain.com/pc/repair/index.php?pcwo=6362"
2022/10/22 20:26:54 [error] 292#292: *917 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught Error: Call to undefined function mb_substr() in /var/www/pcrt/repair/pc.php:2919

You would be best to email PC Repair Tracker, he would know what the error is all about. I’ve installed for clients with no issue on a Cpanel setup. As long as you edit your deps.php file correctly it should all work. I’ve never install on VM or webmin. I would think VM would be a easier system to run on as it setup your webhosting correctly.

hi there and thanks for replying, pc repair tracker is not responding emails or support, idk why. i have edited all deps files and everything is working fine. is just that issue that is driving me kdjfkd.
Still trying to figure this out. thanks

seems like you don’t have the correct php modules
try sudo apt-get install php-mbstring and restart apache

thanks so much, it worked.