We are creating a new brand and create.php file is blank.
This is likely due to some columns not being created.
Login to your MySQL database directly via phpmyadmin or any other method you like, then run the following MySQL queries:
ALTER TABLE campaigns ROW_FORMAT=DYNAMIC;
ALTER TABLE lists ROW_FORMAT=DYNAMIC;
ALTER TABLE apps ROW_FORMAT=DYNAMIC;
ALTER TABLE campaigns ADD web_version_lang VARCHAR(50);
ALTER TABLE lists ADD hide INT(1) DEFAULT 0;
ALTER TABLE apps ADD hide_lists INT(1) DEFAULT 1;
ALTER TABLE apps ADD COLUMN opens_tracking INT (1) DEFAULT '1', ADD COLUMN links_tracking INT (1) DEFAULT '1'
Then try again.
Going forward, please ensure you've granted FULL privileges to the MySQL database user for your MySQL database.