Currently unable to handle this request. HTTP ERROR 500 on a specific page of site

I am getting this error on only a specific url of site i.e:

https://trafficwardenatd.com/abttrafficpolice/learningSlip.php

Rest of my site is working fine. I have tried the following techniques till now and they are not working.

1. create a new .htaccess file.
2. Disable all the plugins.
3. Increase the PHP memory limit.
4. Updated the wordpress wp-admin and wp-includes directories with latest downloaded directories.

Can any one help me to sort out this error?

Thanks