RLI Opportunity Subpanel create not working


currently we have an environment that the customer wants to have opportunities with revenue line items enabled. So what I naturaly did was to enable the subpanel en module in de administration and on top of that changed the opportunity settings to use opportunities and rli's. 

Now when I want to create a new opportunity the only thing I can see is the header of the RLI subpanel but the definition / fields are missing. 

What could be the cause of this? I already copied the necesary files from /modules/RevenueLineItems to custom/modules/RevenueLineItems to see if that would solve anything but unfortunatly it doesnt. 

I hope someone has any idea what this could be. 

p.s. its a 8.0.1. environment.