Previous denied authentications , there is maybe a solution:

We are willing to reopen files for authentication of paintings, denied for any reason in the past, under specific conditions and only for major artists, especially old masters.
Several former authorized experts are denied today, or the authorized expert is changed, or deceased and the new authorized experts do not necessarily use the archives of the former expert.
The Art world is in constant evolution and sometimes revolution, also the Fine Art Appraisal.
By example:
Vlaminck, paintings were recognized by his daughter? Today this is only under the authority of the Foundation Wildenstein, but also this famous institute makes mistakes. Based on my own experience, we can tell that if you come up with unbeatable arguments these gentlemen will recognize the authenticity of your Vlaminck, it takes time and lots of work.

Utrillo, Mr. Petrides denied several paintings, using his monopole rights over the artist works. Several authentic Utrillo paintings were denied, and in particular several fake paintings were authenticated by Mr. Petrides. It was told he went to jail for a while. Luckily Mr. Fabrice showed up one day in an auction room in London where he made a scandal about several paintings that were offered as Utrillo paintings. Fabrice and Petrides are certifying Utrillo works in accordance today.

Picasso, The Committee Picasso (made mistakes?), and is ended since 1993!

Old Masters, All major museums in the world are publishing every decade an update of their possessions, it’s so that a painting attributed to Caravaggio 10 years ago, may be attributed to an famous unknown painter tomorrow. Rembrandt is a good example of this ®evolution, it looks today that 50 % of the Rembrandt’s on display in museums in the world are not by his hand…
We are accepting assignments for reintegration of authenticity if in our opinion, the artwork is defendable (Manifestly fakes or forgeries are excluded for acceptance), with a serious provenance history.
We retrace the complete history of the painting, provide an analytic analyze, a study of the manner this painting was made, radiographic analyze, chemical study of the paint, in one word a complete autopsy of the painting and his context.
These research works are difficult, take a long time to be accomplished, we limit these expertise to paintings with a value (authenticated ) > $ 200,000.00. An average study takes 6 months.
After reviewing your painting we will give you a free proposal