New Post: EDMX designer can't see my EF6 provider

we're moving our EF provider for DB2 for i (i.e AS400) to EF6 (our previous version works fine in EF4 up to VS2012)
Added new config classes and service providers, etc but still EDMX wizard VS2013 (+EF Tools) cannot recognize it when we try to add a model (database first).
Debugging the provider, we can reach the connection to be used (we have a VS package to integrate the provider with VS itself and add connections) then we choose an available connection (or create a new one) but the next step fails saying an EF 6 provider is not found.

We have followed the guides, like "Rebuilding EF providers for EF6" but till now no luck.

Is there something to do to deepen the debugging? Can we debug the designer to clarify why it does not try to call our Service providers?

Thanks
Alberto