I have done a new installation of the develop branch. I get a pop up message showing server error when ever I open a customer profile.
InternalError: (1054, u"Unknown column ‘tabService Level Agreement.customer’ in ‘where clause’")
ERPNext: v12.x.x-develop () (develop)
Frappe Framework: v12.x.x-develop () (develop)
Even i am facing the same issue
As the server error says, there is no column name Customer in tabService Level Agreement.
Please wait for the official release of v12 or else you can alter the table tabService Level Agreement by creating column named as customer.
There is no table named tabService Level Agreement in v12 (Develop). The only thing you can do is wait for release of v12 (Official).
I hope this solves your query/problem.