Since it is your domain that is blank do this query:
UPDATE `mybb_settings` SET `cookiedomain` = '.letsplanmywedding.com'
after doing this: #1054 - Unknown column 'cookiedomain' in 'field list'
Whats your table prefix? (mybb_, forums_, mybb_forums_)
the table prefix is for whole the website. but there are table prefix like forum_category ; mybb_forums so which one i must to change?
The table prefix that is for your forums database tables.
If mybb_ is your table prefix I can't see anything wrong with the query.
UPDATE `mybb_settings` SET `cookiedomain` = '.letsplanmywedding.com'
My table prefix is dimas_plan_wedding , there is not forum prefix, but all are going inside...
Can you open ./inc/config.php
Can you tell me what this line contains?
$config['database']['table_prefix']
e.g mybb_