Kindly take backup of site and try this page sent by dev
I did exactly the above and followed your directions@pankaj#156596
You didn't mention to use a test site, you said it was an option.
As I don't have access to setup a test site.
So I uploaded the file you mentioned after backing up my site in case it crashed i believed.
It didn't crash, but didn't resolve the issue.
If you can please take my backup that I sent to you and try yourself.
You will see the patch doesn't work, sadly.
I did everything you just mentioned;
Please follow this :
1. Take a full backup of website or make a staging site.
2. Install Guru package i sent to you in previous reply
3. Setup the ACL as i asked to do.
4. Buy a course with new student and check.
Still had issue, but again I didn't use a test site, I just uploaded to the main site assuming what you sent me would work and also because I do not have access to setup a test site.
Would you mind taking the backup I sent you in a link previously and seeing if you can find the issue, please?