"Could not load the selected model" error when setting the entry model

I have a "Could not load the selected model" error when setting the entry model for collaboration hub. Anyone seen this and know why it is happening? I've added one user to a user group and I am trying to point the 'entry diagram' at a value chain model (imported from APQC).

I've checked the permissions and the user has 'H' access to the folder where the model is.

Any help is very much appreciated.