See https://www.opensource-socialnetwork.org/wiki/view/2006/how-to-install-and-update-components you missed

10 Finally, click the Enable button

I have installed the HelloWorld files exactly as per the Github instructions. I get the 404 page. Is there an issue with the main system? (See https://mygrworld.com/ossn/hello_custom_template)

Thank you for your help. Strange, I did not do any manual installation.

Just did a fresh installation on your request in the email and it worked fine installation was smooth without any issues. I think you may have installed manually before (not followed installer) I am not sure what was the issue.

You don't need a VPS unless you want a special configurations like video conversion , ffmpeg tools etc.

I have also been told I need a VPS, thank you.

open your ossn database with phpmyadmin and click the Structure tab. The table names must look like this:

For some reason your host seems to add the prefix mygrsolu_ossnnew, though. That's why the query fails.
Did you configure anything special to achieve automated prefixing? If so, please switch off that option.

In checking the PHP log, I get this:

[20-Feb-2023 15:25:08 Europe/London] PHP Fatal error:  Uncaught OssnDatabaseException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'mygrsolu_ossnnew.ossn_site_settings' doesn't exist 
 SELECT * FROM ossn_site_settings as s  WHERE((s.name IN ('theme','site_name','language','cache','owner_email','notification_email','upgrades','display_errors','site_key','last_cache','site_version')))   ;  in /home/mygrsolu/mygrworld.com/ossnnew/classes/OssnDatabase.php:148
Stack trace:
#0 /home/mygrsolu/mygrworld.com/ossnnew/classes/OssnDatabase.php(281): OssnDatabase->execute()
#1 /home/mygrsolu/mygrworld.com/ossnnew/classes/OssnSite.php(59): OssnDatabase->select()
#2 /home/mygrsolu/mygrworld.com/ossnnew/libraries/ossn.lib.system.php(29): OssnSite->getAllSettings()
#3 /home/mygrsolu/mygrworld.com/ossnnew/system/start.php(39): include_once('/home/mygrsolu/...')
#4 /home/mygrsolu/mygrworld.com/ossnnew/index.php(12): require_once('/home/mygrsolu/...')
#5 {main}
  thrown in /home/mygrsolu/mygrworld.com/ossnnew/classes/OssnDatabase.php on line 148