The two churches are covenanted to achieve full visible unity, and have made a great deal of progress is working together. But they have come up against (not for the first time) the problem of interchangeability of ministers.
The CofE requires the existence of the historic episcopate in a church with which it unites (under the Chicago-Lambeth Quadrilateral) and requires as a matter of order that priests ordained by bishops in apostolic succession preside at sacraments in CofE churches. The Methodist Church of GB has accepted in principle that it will receive the gift of personal episcope, but has shied away from attempts to clarify and formalise that. They are, of course, reluctant to jump through Anglican hoops which they may see as disparaging the orders of their present ministers.
The way ahead is not clear, although based on the acceptance by the CofE in bilateral discussions that the ruling body of British Methodism, the Conference, exercises episcopal oversight in the Methodist Church, the most likely solution is for each President of the Conference to be consecrated a bishop of the Church Catholic (as Anglicans would see it). This would not necessarily be a CofE bishop doing the initial consecration (which might be a sensitive point) since I understand the Methodists are in communion with other churches with (it is believed) apostolic succession.
Full details here:
anglican-methodist.org.uk