Hello.Try different PHP versions like 7.2-7.4.Check the permissions for files and folders on the hosting.Try deleting all site files from the hosting and re-uploading it.

dear sir i am all file deleting form my website hosting and upload again all file and change the php version 7.2 or 7.4 same error 500 show ( how to check the permissions for files and folders on the hosting ) please tell me how to solve this problem thanks

please see the file how to solve this 

I sent a notification about your question to the company employees, expect an answer from them here in the comments.

ok sir thank you for understanding my problem i am waiting for solve this problem 

Hello Jebran

If the error that pops up as soon as you enter the /admin section is error 500, it is very probable that a bad PHP version is the cause.

Please contact your hosting provider and have them verify correctly the PHP version running for your website. Additionally, ask them to report to you the exact error that is generated. ERROR 500 is a generic code for an error that only the web hosting can see.

Let me know this information here so that I might verify this further

Thank you

Stefano

hello sir i am contact the hosting you ask me As I have checked, there is a following error in the error-log file: [23-Mar-2021 13:55:31 America/New_York] PHP Warning: require_once(../res/x5engine.php): failed to open stream: No such file or directory in /home/webbzmar/public_html/admin/includes.php on line 3 [23-Mar-2021 13:55:31 America/New_York] PHP Fatal error: require_once(): Failed opening required '../res/x5engine.php' (include_path='.:/opt/alt/php74/usr/share/pear') in /home/webbzmar/public_html/admin/includes.php on line 3 .
There is no x5engine.php file in the public_html/res folder. Please contact your developer for further assistance.

i have attach admin error log file please see it

Hello Jebran

If the error is this, it should be easily solved.

Go to Step 5 and export the project completely, not just the latest updates:

Try this out and let me know if it works

Thank you

Stefano