Symptoms
In Home > System > Settings> Notifications > Common Notification Settings the URL to the logo is set in a format like:
https://branded_url/static/skins/default/custom/images/logo.gif
It used to work correctly but after upgrade to OSA 7.0 the url shows 404 Not found error, as a result notifications are sent without logo.
Cause
The link with logo.gif has been configured a while ago, when skin version 2 was used. Since OSA 7.0 support of skin v2 was dropped in webgate, as a result the corresponding rewrite rules were removed from branding_htaacess files making such URLs inaccessible.
Resolution
Change URL to logo to:
https://branded_url/webgate/static/skins/v3/images/logos/panel-logo.png