Hard to describe, but look at the picture please. There is just no opportunity card on main navigation bar, so unable to get into opportunity related activities, orders or quotes etc. In the past I recovered from jscript error as described here https://social.microsoft.com/Forums/en-US/1894631c-a2a9-49ac-a858-76ffa0cfe5a6/crm-2013-strange-formonload-error-message-in-opportunity?forum=crmdevelopment. As mentioned I manually fixed clientincludes section, and onload error disappeared. I assume there is another error in xml...
Best Regards