You're using new version of wpForo addon on old version of wpForo. Please don't do that. Just update wpForo to latest 1.4.5 version then install the Ads manager addon.
This error comes from Ads Manager addon, connect through FTP to your website file system and delete the ads manager addon folder. Then update wpForo to latest version and install the addon again. Make sure you don't have old customized forum template files in WordPress active theme /wpforo/ folder.