04-24-2021, 03:34 PM
Also important to check in settings.php for cookies so the cookies setting can be changed to match the URL. And of course needless to say - make a very good backup of both Forum and database first before you begin the changes. And then close the Forum in Board Online/Offline. 
Here are some guidelines for cookies settings by one of the mybb forum staff - according to his experience this is where most of the problems occur when site settings have been changed - when the site settings are changed it's most important to change the cookie settings too. Note specially that there is a different domain path setting for /forum than for domain only:
https://community.mybb.com/thread-42123.html
You also need to make the changes in Admin Panel. Admin Panel/Configuration/Site Details. As with the settings you have to make changes for both the URL as well as the cookie domain and cookie path in the Admin Panel/Configuration/Site Details as per the above recommendations for cookie settings for domain/forum.
I'd have been tempted to make the changes in the Admin Panel Configuration Site Details first and see how it goes. Maybe it automatically updates the settings.php file. Or maybe one has to do both the Site Details Configuration change as well as the inc/settings.php. Maybe @Mashiro or @Dynamo or @TrK can advise in this instance.
Here are some guidelines for cookies settings by one of the mybb forum staff - according to his experience this is where most of the problems occur when site settings have been changed - when the site settings are changed it's most important to change the cookie settings too. Note specially that there is a different domain path setting for /forum than for domain only:
https://community.mybb.com/thread-42123.html
You also need to make the changes in Admin Panel. Admin Panel/Configuration/Site Details. As with the settings you have to make changes for both the URL as well as the cookie domain and cookie path in the Admin Panel/Configuration/Site Details as per the above recommendations for cookie settings for domain/forum.
I'd have been tempted to make the changes in the Admin Panel Configuration Site Details first and see how it goes. Maybe it automatically updates the settings.php file. Or maybe one has to do both the Site Details Configuration change as well as the inc/settings.php. Maybe @Mashiro or @Dynamo or @TrK can advise in this instance.